馬來酸酐接枝PPPE共混物及其木塑復合材料(完整版)實用資料

馬來酸酐接枝PPPE共混物及其木塑復合材料（完整版）實用資料(可以直接使用，可編輯完整版實用資料，歡迎下載）

第46卷第1期林業(yè)科學V01.46,N。.12021年1月SCIENTIASILVAESINICAEJan.,2021馬來酸酐接枝PPPE共混物及其木塑復合材料（完整版）實用資料(可以直接使用，可編輯完整版實用資料，歡迎下載）馬來酸酐接枝PP/PE共混物及其木塑復合材料木高華王清文王海剛宋永明(東北林業(yè)大學生物質材料科學與技術教育部重點實驗室哈爾濱150040摘要:通過聚丙烯(PP與聚乙烯(PE機械混合來模擬廢舊塑料混合物,利用馬來酸酐(MAH對PP/PE混合.物進行接枝改性,然后以接枝共混物作為基體與木纖維復合制備木塑復合材料。通過對比接枝前后的紅外光譜圖,證明MAH已成功接枝在PP/PE共混物上。力學測試結果顯示:基體經過接枝改性后,復合材料的彎曲強度和無缺口沖擊強度均大幅度升高,當MAH用量為1%時,彎曲強度提高了50.4%,無缺口沖擊強度提高了90.8%,而以廢舊塑料為原料制備的復合材料的彎曲強度和無缺口沖擊強度分別提高40.2%和53.4%。微觀相形態(tài)分析表明:通過接枝改性不僅改善了PP/PE共混體系的相容性,同時也顯著改善了木纖維與PP/PE共混物之間的界面結合狀況,因而宏觀上表現為力學性能提高。這表明,共混接枝改性方法可能是利用混合廢舊塑料制備高性能木塑復合材料的一條可行途徑。關鍵詞:馬來酸酐;接枝;PP/PE共混物;木纖維;木塑復合材料中圖分類號:TQ321.5文獻標識碼:A文章編號:1001—7488(202101—0107—05MaleicAnhydrideGraftedPP/PEBlendandTheirCompositeswithWoodFiberGaoHuaWangQingwenWangHaigangSongYongming(KeyLaboratoryofBio—BasedMaterial&ienceandTechnologyofMin曲tryo,Education,NortheastForestryUniversityHarbin150040Abstract:Inthispaper,thewasteplasticmixturewassimulatedbymechanicallymixingpolypropylene(PPandpolyethylene(PE,thePP/PEmixturewasblendedandatthesametimegraftedwithmaleicanhydride(MAHbyreactiveextruding,andthewoodplasticcompositeswaspreparedwiththegraftedblend,whichwasused踮matrix,andwoodfiber.BycomparingtheinfraredspectrogramofthegraftedPP/PEblendwiththatoftheunmodifiedblend.itprovedthatMAHwasgraftedontoPP/PEblend.Mechanicaltestingresultsshowedthattheflexuralstrengthandun-notchedimpactstrengthofthecompositeswerebothsignificantlyenhancedbytheblending-graftingmodificationofplasticmixture.WhenMAHdosagewas1%。theflexuralstrengthincreased50.4%andtheun?notchedimpactstrengthincreased90.8%.andtheflexuralstrengthandtheun-notchedimpactstrengthofthecompositepreparedfromwasteplasticincreased40.2%and53.4%respectively.Themicro—morphologicalanalysisindicatedthatwithmodificationthecompatibilityofPPandPEintheblendsystemwasimprovedandtheinterfacialadhesionbetweenwoodfiberandPP/PEblendwasalsoenhanced,thusitexhibitedtheelevationofthemechanicalproperty.Thisblending-graftingmodificationmethodcanbeconsideredasafeasibleapproachtoexpandtheu8eofmixingwasteplasticsinthemanufactureofhishperformancewoodplasticcomposites.Keywords:mahicanhydride(MAH;grafting;PP/PEblend;woodfiber;woodplasticcomposites利用廢舊塑料與木質纖維材料制造木塑復合材料是材料循環(huán)利用的有效方法之一,同時也降低了木塑復合材料的原料成本,已成為當今木塑復合材料研究的熱點(郭文靜等,2006;Clemons,2002;Okamoto,2002。但是大多數廢舊塑料都是以多種塑料的混合物形式存在的,塑料的分類是回收過程中所面臨的難題之一,由此帶來的成本增加問題也影響了木塑復合材料產品的市場競爭力。然而直接利用混合廢舊塑料制備木塑復合材料,可以減少塑料分類帶來的麻煩。為了實現利用混合廢舊塑料制備高性能木塑復合材料,首先必須解決廢舊塑料的再生改性問題,包括不同塑料組分之間的相容性差、不同塑料組分因熔融溫度相差大而難以在適當的溫度下共熔、因降收稿日期:2021一06一05。基金項目:。863”項目(2002AA245141;國家農業(yè)科技成果轉化資金項目(2006GB23600450。?王清文為通訊作者。林業(yè)科學46卷解而性能劣化的廢舊塑料如何增強等問題。此外,在木纖維填充量較高(≥50%的情況下,非極性的塑料基體與極性的木纖維之間的相容性很差,氫鍵的作用也導致木纖維之間的作用力增強,從而影響木纖維在聚合物基體中的分散,所制得的木塑復合材料性能較差(Oksmaneta1.,1998;洪浩群等,2007。因此,改善塑料基體與木纖維之間的界面相容性也是制備性能優(yōu)異的木塑復合材料的關鍵。本研究的目的在于探索一種新的技術方法,改善混合塑料各組分之間、塑料與木纖維之間的相容性,為混合廢舊塑料的高效利用提供可行的途徑。通過聚丙稀(PP與聚乙烯(PE共混來模擬廢舊塑料混合物,利用馬來酸酐(MAH對PP/PE混合物進行接枝改性,然后以接枝共混物作為基體與木纖維復合制備木塑復合材料。采用同樣的改性方法,也對混合廢舊塑料進行了研究,以驗證此方法的可行性。利用紅外光譜法對接枝產物進行表征,采用掃描電子顯微鏡(SEM考察改性前后PP與PE之間、木纖維與PP/PE共混物之間的界面相容性,同時通過力學試驗分析塑料混合物MAH接枝改性對木塑復合材料力學性能的影響。1材料與方法1.1材料聚丙烯(PP,型號T30S,中國石油大慶石化公司生產;高密度聚乙烯(HDPE,型號2200J,中國石油大慶石化公司生產;廢舊塑料混合物(經FTIR分析,其主要成分為PP和PE,市購;馬來酸酐(MAH,分析純,天津市博迪化工生產;過氧化二異丙苯(DCP,分析純,天津市博迪化工生產;楊木纖維,由課題組木塑復合材料原料基地提供;聚乙烯蠟,市購。1.2設備及儀器1.3接枝物的制備本文采用反應擠出的方法,在雙螺桿擠出機中進行熔融接枝反應(王清文等,2021。首先,按一定配比分別精確稱量MAH和DCP(10:1,然后將其在研缽中研磨以便混合均勻。將MAH,DCP混合物加入到PP/PE(80/20混合物中,通過攪拌使其均勻地分散,然后將混合物料加入雙螺桿擠出機料斗中,在DCP引發(fā)下進行熔融接枝反應。PP/PE共混接枝產物冷卻后,粉碎備用。1.4木塑復合材料的制備裹1擠出工藝參數Tab.1Extrudingparameters1.5測試方法第1期高華等:馬來酸酐接枝PP/PE共混物及其木塑復合材料取微量純化的接枝產物粉末,與光譜純KBr粉末混合研磨后,壓制成透明薄片,進行傅里葉變換紅外光譜測定。掃描范圍400cm“到4000cm~,掃描次數40次?min~。同時,對未接枝的PP/PE混合物也進行了掃描作為參照。其木塑復合材料試樣分別放入液氮中進行充分冷卻,然后使其快速脆斷,脆斷表面經噴金處理后,利用掃描電子顯微鏡(SEM在加速電壓為15kV下觀察其表面形態(tài),并拍攝不同倍數的照片。測試參照ASTM標準中塑料彎曲試驗標準方法(ASTMD790—03,跨距為64mm,加壓速度為2mm?min~;無缺口沖擊強度測試,采用塑料測試國家標準(GB/T1043—1993進行簡支梁擺錘沖擊試驗,跨距為60mm,沖擊速度為2.9m?s~,擺錘能量為2J。每一組試件5個測樣。2結果與討論2.1接枝產物的紅外光譜表征圖1是接枝產物與未接枝PP/PE共混物的紅外光譜圖。通過對比可以看出,接枝產物的FTIR譜圖上在1787.7cm。處出現振動吸收峰,這是酸酐中羰基的特征吸收峰。由于接枝物已經被純化,確定不含游離的接枝單體,即樣品中沒有馬來酸酐單體的存在,所以觀察到的1787.7cm“處的吸收峰只可能是已接枝上的馬來酸酐的特征吸收峰,故可確認MAH已成功接枝在PP/PE上了。聚烯烴共混物的接枝反應極其復雜,產物的精細結構鑒定十分困難,接枝產物中PP接枝產物與PE接枝產物的比例、馬來酸酐基團的分布規(guī)律等細節(jié)問題可能對其性能有影響,因而需要進一步展開圖1PP/PE共混物的紅外光譜Fig.1TheinfraredspectrogramofPP/PEblend深入研究。2.2接枝產物的微觀相形態(tài)分析對于共混體系來說,形態(tài)結構和界面性能是影響其性能的重要因素。利用掃描電子顯微鏡(SEM對共混物的斷面進行觀察分析,從而考察共混物中兩組分的相容情況,是一種最直觀的材料分析方法(高歌等,1999。從圖2a可以看出,在未改性的PP/PE(80/20混合物中,形成典型的連續(xù)相與分散相并存的“海一島”結構(舒文藝等,1992,PE以球狀分散在連續(xù)相PP中,粒徑分布較寬,且表面光滑,兩相之間的界面也很清晰,斷裂后留下許多空洞,說明PE與PP之間粘著力差,體現了典型的不相容共混體系的形態(tài)特征。經過接枝改性后,共混物的微觀相形態(tài)發(fā)生了明顯的變化(圖2b。從圖中可以看出,共混物中分散相(PE相的粒徑變小,粒徑分布也變窄,兩相之間的界面已經變得很模糊,斷裂后留下的空洞變少,粘結程度明顯增強。這說明通過接枝改性改善了PP/PE共混體系的相容性。a.未改性UnmodJfieclb改性后Modified圖2PP/PE共混物斷面的SEM照片(3ooo×Fig.2SEMmicrographofthefracturedsurfaceofPP/PEblends(3000×110林業(yè)科學46卷2.3木塑復合材料的力學性能示,塑料基體經過改性后,復合材料的彎曲強度得到了顯著提高,并且在MAH用量為1.0%時達到最大值,與基體未改性的復合材料相比提高了50.4%。然而,隨著MAH用量的繼續(xù)增大,復合材料的彎曲強度又開始下降。當木纖維與未改性的塑料直接復合時,由于兩者的相容性較差,木纖維在基體中不能很好地分散,在成型加工過程中木纖維沒有被塑料基體充分潤型嘲冒舯6.56.0s.5墓5.o囂4.54.0MA嗍+彎曲強度Flexural蜘即gtIl濕,因而界面結合較差,木纖維沒有起到增強作用。而經過接枝改性的PP/PE共混物中引入了極性的酸酐基團,與木纖維表面上的羥基發(fā)生酯化反應而通過共價鍵連接,降低了纖維的表面能,并提高了木纖維在基體樹脂中的分散性,因而能改善木纖維與基體之間的界面結合(Balasuriyaeta1.,2001。然而,隨著MAH用量的增多,基體中存在過多的極性酸酐基團,致使大分子鏈的運動受到限制,基體的流動性降低,因而不能很好地對木纖維進行潤濕,導致強度開始下降?！痡疆}MAH,%+彎曲模tF|exuralmodtlJu￥圖3不同MAH用量的復合材料的彎曲性能與沖擊強度Fig.3TheflexuralpropertyandimpactstrengthofthecompositeswithdifferentMAHdosage木塑復合材料彎曲模量的變化也表現出一定規(guī)律性,隨著接枝過程中MAH用量的增加,復合材料的彎曲模量開始呈下降趨勢,之后又逐漸升高。根據混合法則,復合材料中的各組分對模量都存在著貢獻,當MAH用量較低時,由于降解使塑料的分子質量降低,導致復合材料的模量下降。隨著MAH用量升高,接枝逐漸處于優(yōu)勢,不僅塑料基體的模量升高,而且由于接枝到聚烯烴上的酸酐基團與木纖維上的羥基以化學鍵結合,增強了木纖維與基體之間的界面結合,使復合材料獲得了較高的剛性,因而彎曲模量呈升高的趨勢。對于基體未改性的復合材料,木纖維和基體樹脂之間僅靠微弱的物理作用結合,當材料受到外力作用時,應力無法從木纖維傳遞到基體,會在這些微弱的界面結合處形成應力集中,從而導致材料在相對較小的外力作用下就發(fā)生斷裂(Lueta1.,2005。基體經過改性后,在聚烯烴分子鏈上引入了極性酸酐基團,它與木纖維中的羥基將以共價鍵或氫鍵結合,兩者之間形成了一定厚度的界面層,進而提高了界面結合強度。材料在承受外力作用時,界面層能將沖擊能量平穩(wěn)地從木纖維傳遞到基體樹脂中,這樣就很好地吸收了外界的能量,使材料的沖擊強度提高(王海剛等,2006。然而,當MAH用量相對過多時,多余的接枝聚烯烴自身將發(fā)生纏結,與木纖維和基體之間的作用力相比,這種纏結作用很容易破壞。當受到外力作用時,將率先在微弱的結合處發(fā)生斷裂,造成復合材料的沖擊強度下降。采用同樣的方法對混合廢舊塑料進行改性,制得的木纖維/廢舊塑料復合材料的力學性能也得到了較大的提高,同樣在MAH用量為1.0%時,彎曲強度和沖擊強度都達到最大值,與基體未改性的復合材料相比,分別提高了40.2%和53.4%。2.4木塑復合材料的微觀相形態(tài)分析對于木塑復合材料來說,木纖維與塑料基體之間的界面結合是影響其性能的至關重要的因素之一。通過SEM觀察,可以直觀地分析界面結合情況,也可為判斷木纖維與基體之間相容性是否得到改善提供依據(丁筠等,2004;劉玉慧等,2007。圖4a為基體未經過改性的木塑復合材料的SEM照片,材料的斷面顯示木纖維在聚烯烴共混物基體中分散不是很均勻,可以明顯地觀察到纖維拔出的跡象。從微觀結構分析,復合材料中木纖維和基體之間的界面很明顯,纖維相的“相疇”明顯,兩∞":8弱如帖∞第1期高華等:馬來酸酐接技PP/PE共混物及其木塑復合材料相之間的結合不是很好,這與前面力學性能比較中基體未進行接枝改性的復合材料的強度較低的結果是相符合的。而以接枝改性的PP/PE共混物作為復合材料基體,復合材料中纖維相分散均勻性提高。觀察圖4b可以看出纖維被拔出的跡象明顯減少,大部分木纖維受力時發(fā)生斷裂并且殘留在基體中。這說明木纖維與基體之間的界面結合增強,兩相的相容性得到了有效改善,因而宏觀表現為材料具有較高的力學性能。a.基體未改性MatrixtmmodJfiedb.基體經過改性Matrixmodified圖4木塑復合材料斷面的SEM照片(200×Fig.4SEMmicmgraphofthefracturedsurfaceofthewoodplasticcomposites(200×3結論1通過對比接枝前后的紅外光譜圖發(fā)現,接枝產物在大約1787.7cm“處出現羰基的特征吸收峰,證明MAH已成功接枝在PP/PE上;微觀相形態(tài)分析表明,接枝改性改善了PP/PE共混體系的相容性。2木塑復合材料的力學測試結果表明,基體經過接枝改性后,復合材料的彎曲強度和無缺口沖擊強度都有較大的提高,采用同樣的方法對混合廢舊塑料進行改性后,木纖維/廢舊塑料復合材料的力學性能也得到較大提高;通過對復合材料的微觀相形態(tài)分析可知,對基體進行接枝改性改善了木纖維和PP/PE共混物之間的界面結合。上述結果表明,采用此種改性方法對混合廢舊塑料進行改性,是混合廢舊塑料高效利用、制備高性能木塑復合材料的一種可行的途徑。參考文獻展.塑料科技,35(8:118—123.polyethylenecomposites:couplingagentperformance.J0umalofAppliedPolymerScience,96:93—102.(42:112—115.modifiedpolypropylenewoodflourcomposites.JournalofAppliedPolymerScience,67(9:1503—1513.(責任編輯石紅青維普資訊://cqvip?６６?３材料科學與工程學報２０年８０６月ｎ６Ｐｎｅ，ＨｈＴ．Ｊ．ＣｍｏｉｓＳｉｃｎｅｈｏｇ，］ａｄｙＲ．ａｎＨ．［］ｏｐｓｅｃｅｅａｄＴｃｎｌｙｔｎｏ●值預報［］北京航空航天大學學報，０２５２）５３５５Ｊ．２０，（８：６６．［１龐寶君，善義，嚴４］杜２５．ｌ１９，５９６６：１—１０．６１７勇，．三維四向碳．氧編織復合材等環(huán)［７韓其睿，嘉祿，學明．Ｊ．合材料學報，１９，１（）７１］李李［］復９６３３：６—料剪切力學性能實驗研究［］實驗力學，１９，２１）２９Ｊ．９９（４：０［２龐寶君，杜善義，韓杰才，等．三維四向編織碳．氧復合材４］環(huán)８ｏ．［８ＣｈｎＬ．，Ｔａ．Ｍ．，ＣｈｙＣ．Ｌ．Ｍｅｈｎｉａａｙｓｓｏ３Ｄｂｒｉｅ１］ｅｏＸｏｃａｃａｌｉｆｌｎａｄｄｃｍｏｉｓｂｅｆｉｕｐａｅｅｍｎｍｔｄＪ．ＣｍｏｉｓｏｐｓｅｙｔｎｅｍＭｈｓｌｅｔｅｈ［］ｏｐｓｅｔｈｉｔｅｏｔＳｉｎｅａｄＴｃｎｌｇ，９９．５ｃｅｃｅｈｏｏｎｙ１９９：２８—２９．３３３１ｅＬ．ｏＸｏｈｃｏｓｒｃｕｅｏｈｅ．［９Ｃｈｎ．Ｔａ．Ｍ．．ＣｈｙＣ．Ｌ．Ｏｎｔｅｍｉｒ－ｔｕｔｒｆｔｒｅ１］料實驗研究［］復合材料學報，１９，（６：１６１１Ｊ．９９４１）３４．［３梁軍．三維編織復合材料力學性能的細觀研究［］哈爾４］Ｄ．濱工業(yè)大學，１９．９６ｄｎｉａｒｄｄｐｒｒ［．ＣｍｏｉｓＳｉｎｅａｄｉｓｎｂａｅｅｆｍｓＪ］ｍｅｏｌｉｏｏｐｓｅｃｅｃｎｔＴｃｎｌｇ，１９ｅｈｏｏｙ９９，５９：３１—４４．９Ｏ［４梁４］一軍，善義，杰才．Ｊ．合材料學報，１９．（４：０杜韓［］復９７１１）１１ｌＯ７．［０龐寶君，２］杜善義，杰才．三維四向編織復合材料細觀組織及韓分析模型［］復合材料學報，９９１（）３１９Ｊ．１９，６３：１５３．［１徐孝誠，２］孫德海，小平．三維編織復合材料細觀結構的幾何黃學分析［］強度與環(huán)境，１９．２：３４．Ｊ．９９（）７３［２黃小平，良新，孝誠．合材料三維四向矩形編織物角柱２］孫徐復結構研究［］復合材料學報，０１４１）１１．Ｊ．２０．（８：１５［３黃小平，良新，孝誠．２］孫徐四向矩形編織復合材料單胞的新劃分方法［］纖維復合材料，０１３１）５１．Ｊ．２０，（５：１７［４２］ＭａｉｏＴｄ，ｔｄｓｉｋｋａａａａｈＵｏｕ，ＡａＮａａ，ｔ１．ｓｒｃｕｅａｄｚｍｉｓｍｉｋｉｅａｔｔｒｎｕ【５Ｌｉ，ＣｉＹ．Ｊ，Ｋ．Ｋ．Ｊ．ｄａｃｓｉｎｉｅｒｇ４ｅＣ．ａＪ．ｏＦ［］ＡｖｅｎＥｇｉｎｎｎＳｆａｅｌ９１ｌ７一ｌ４．ｏｔｒ，９２，４：８ｗ９【６ＳｒａＲ．Ｋｉｎ，ＥｃＦａｃ．Ｊ．ｏｐｓｅＳｉｃｎ４ｕｙ，ａｄｄＪｌｉｉｉｒｒｏ［］ＣｍｏｉｓｃｎｅａｄｎｔｅＴｈｏｏｙ。ｌ９．７ｌｌ一３５．ｃｅｎｌｇ９７５：９０【７ＪＣｈｎＬ．ＴｏＸ．Ｍ．ＣｏＣ．Ｌ．Ｍｅｈｉａａａｙｉｆ３４ｅ，ａ，ｈｙｃａｃｎｌｓｓＤｎｌｏｂａｅｏｐｓｅｙｔｅｆｉｕｉｈｓｌｎｍｔｏ［］ｒｄｄｃｍｏｉｂｈｎｔｍｌｐａｅｅｍｅｔｅｄＪ．ｉｔｓｉｅｔｅｈＣｍｐｓｔｉｎｅａｄＴｃｎｌｇ，１９ｏｏｉＳｅｃｓｅｃｎｅｈｏｏｙ９９，５９：２８３３—２９．３１【８ＪＺｎａ，ＷｕＩｎｚｉＧｕｉｃｅｇ．ＭｅｈｎｃａｙｉｏＤ４ｅｇＴｏｊ．ｈ，ｏＬ－ｈｎｃａｉａａｌｓｓｆ３ｌｎｂａｅｏｐｓｅ：ｎｔｅｍｎｍｅ［］ｏｏｉｔｃｒｒｄｄｃｍｏｉａｆｉｌｅｔｏｌＪ．ＣｍｐｓｅＳｒｔｅｉｔｓｉｅｅｄｔｕｕｓ２０６３９—４４．０４．４：９Ｏｍｃｉｅｂａｄｎｒｃｄｒｏｏｐｅｓｕｒｂａｄｔｖｒｕａｈｎｒｉｇｐｏｅｕｅｆｃｕｌｄｑａｅｒｉｓｗｉｉｈａｉｓｏｃｏｓｅｔｎ【ＪＣｍｏｉｓａｔｒｃｏｓＪ．ｏｐｓｅ：ＰｒＡ，２０，２４５—１８．ｓｓｉｔ０１３：１８４９［９劉振國，陸４］一萌，麥漢超，等．三維四向編織復合材料彈性［５ＷａｇＹ．Ｏ．ＷａｇＡ．ＳＤＪ．ｏｐｓｅｉｃｎ２］ｎ，ｎ．．［ＣｍｏｉＳｅｅａｄＪｔｃｎｓＴｃｎｌｇ，１９５５５—５６．ｅｈｏｏｙ９４，１：７８模量數值預報［］北京航空航天大學學報，００２（６：８Ｊ．２０．２）１２ｌ５．８［６ＷａｇＹ．Ｏ．ＷａｇＡ．．Ｄ【ｍｅｃｎＳｃｔｏｃａｉ２］ｎ，ｎＳ．Ｊ．ＡｒａｏｉｙｆＪｉｅＭｅｈｎａｃｌＥｎｉｅｒ，９５，５１１—１６．ｇｎｓ１９６：５６［Ｏ劉振國，子興，陸萌．維四向編織復合材料剪切性能５］盧三的數值預報［］復合材料學報，００，７２：６６．Ｊ．２０１（）６９【ｌＴｇＺ．Ｘ．Ｐｓｅ．Ｍｅｈｎｃｆｔｅ．ｍｎｉｎｒｄｄ５Ｊａｎ，ｏｆＲｌｃａｉｏｈｅｄｅｏａｂａｅｓｒｉｓｌｉｓｒｃｕｓｆｒｃｍｐｓｔｔｒｓＰｅｉｔｎｆｈｌｓｉｄｕｉｔｔｒｏｏｉｍｅａ：ｒｄｃｉｏｔｅｅａｔｍｏｌｕｅｏｅａｉｌｏｃ［７ＷａｇＹ．Ｏ．ＷａｇＡ．Ｓ．Ｊ．ｐｌｄＣｍｏｉａｒｓ２］ｎ，ｎ．Ｄ［］ＡｐｅｏｐｓｅＭｔａ．ｉｔｅｌｉ１９．１１１一ｌ２．９７４：２３［８陳２］利，嘉檬，李學明．三維四步法圓形編織結構分析李【ｏｏｉｔｃｕｓ０ｌ５：４ｌ５．Ｊ．ＣｍｐｓｅＳｕｔｅ，２０，ｌ５一４７Ｊｔｒｒ１２Ｔｎ，．Ｐｓｅ５ａｇｚｏｄＸ．Ｒ．ＭｅｈｉｓｏｈｅｄｅｓｎｒｉｅＪｃａｃｔｅ－ｉｎｉａｂ８ｄｎｆｒｍｏｌｄｓｒｃｕｅｆｒｃｍｐｓｔｍｔｒｓＡ：Ｎｏｌｎａｆｉｅｅｅｔｔｔｒｓｏｏｏｉｕｅａｅａｉｌｎｉｅｒｉｔｎｅｌｍｎ［］復合材料學報，０３２（０：６８．Ｊ．２０，２）７Ｏ［９馬文鎖，２］馮偉．三維編織復合材料及其構件可變微單元分析模型［］復合材料學報．２０．０Ｊ．０５１．［Ｏ馮３］偉，馬文鎖．三維編織材料幾何結構群論分析［］科學Ｊ．通報，０５５（０．２０，０２）ｅｓｅｓｎｔｎｏｕｕｆａｔｒｅｄｍｅｓｏａｂａｄｌｒｌ［１ＫｏＦＫ．Ｔｎｉｔｅｇｈａｄｍｄｌｓｏｈｅ．ｉｎｉｎｒｉ３］ｄｆｍａｏａｓＪ．Ｃｍｏｉｔｃｕｓ０１５：４１ｅｒｔｎａｌｉｏｉｎｙｓ［］ｏｐｓｅＳｕｔｅ，２０．１５ｔｒｒ４７．５【３Ｔｎ．Ｘ．ｏｄ５ａｇｚＪ，ＰｓｅＲ．Ｍｅｈｉｈｅ．ｉｅｓｎｂａｅｃａｃｏｔｅｄｎｉａｒｄｄｎｓｆｒｍｏｌｉｓｒｃｕｅｒｃｍｐｓｔｔｒａｓｐｒ：ｆｂｃｔｃｕｅｎｄｆｒｔｔｒｓｆｏｏｉｍｅｌａｔｕｏｅａｉＩａｒｓｕｔａｂｅｉｒｒｉｃｍｐｓｔｌ．ＩｏｏｉＡＪｎ：ＷｈｔｅＭ，ｅｅｉｙＪｎｄ．ＣｏｏｓｅＭａｅｉｓｅｔｇｍｐｉｔｒａ：Ｔｓｎｔｌｉｖｌｍａｔｎ．ｏｐｓｅＳｒｃｒｓ００４：５４９．ｏｅｆｃｏｌＣｍｏｉｔｔｅ２０．９４ｌ５ｕｒｉＪＪｔｕｕ【４ＴｇＺＸ．ＰｓｅＲ．Ｍｃａｉｆｔｅ－ｉｅｓｏａｒｄｄ５ａ．，ｏｆＪｎｌｅｈｎｓｏｈｅｄｍｎｉｌａｅｃｒｎｂｉｓｒｃｕｅｏｏｏｓｔｌｒｓＰｒＩ：ｐｅｉｔｎｆｔｅｌｔｔｔｒｆｒｃｍｐｉｍｉｅｉａｔＩｕｓｅｌａｌｒｄｃｉｏｈｅａｉｏｓｃａｄｅｉ［．Ｐｉｄｌｉ：ＡｅｃｎｏｉｙｏｅｔｇｎＤｓｎＣＪｇ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catalystsupport.Third,theyhavehighthermalandelectricconductivity22:thehighthermalconductivityofgrapheneisbeneficialtothecon-ductionanddiffusionoftheheatgeneratedduringcatalyticreac-tions,especiallyforstronglyexothermicreactions;thehighelectricconductivityofgraphenemakesthematerialagoodcandidateforelectrocatalystsorelectrocatalystsupports.Fourth,theyofferaset-upinwhichtocombinetheoreticalresearch,modelresearchandrealisticapplicationsincatalysis:itispossibletocharacterizetheactivesitesongraphenebyhigh-resolutionimagingtoolssuchastransmissionelectronmicroscopy(TEMandscanningtunnellingmicroscopyevenduringthereactionprocess,whichischallengingfortraditionalcomplexcarbonmaterialssuchasactivatedcarbon.Theelectronicstructureofgraphene,however,presentsbothchallengesandopportunitiesforcatalyticapplications.Thechal-lengesoriginatefromthefactthatgrapheneisazero-overlapsemi-metalwithquasiparticlesobeyingalineardispersionrelation19,23,resultingintheverylowdensityofstatesattheFermilevelfortypicaldopinglevels(zeroattheDiracpoint.Therefore,pristinegrapheneisinertincatalysis.Buttheverysamefactprovidesnewopportunities,astheelectronicpropertiesofgraphenecanbeeasilytunedbyintroducingperturbations,offeringpossibilitiestoinducecatalyticactivityinthematerial.Therearevariousroutestotunetheelectronicstatesofgra-phene.(1Thesizeeffect:abandgapisopenedintheelectronic1StateKeyLaboratoryofCatalysis,iChEM,DalianInstituteofChemicalPhysics,ChineseAcademyofSciences,ZhongshanRoad457,Dalian116023,China.2SchoolofPhysicsandAstronomy,UniversityofManchester,OxfordRoad,M139PLManchester,UK.3StateKeyLaboratoryofPhysicalChemistryofSolidSurfaces,iChEM,DepartmentofChemistry,CollegeofChemistryandChemicalEngineering,XiamenUniversity,Xiamen361005,China.*e-mail:Konstantin.Novoselov@manchester.ac.uk;zqtian@;xhbao@dicp.acspectrumofgraphenenanoribbonsowingtothequantumconfine-menteffect,andthesizeofthegapwillincreasewhendecreasingthesizeofthenanoribbon24,25.(2Thelayereffect:theelectronicstructureofgraphenestronglydependsonthenumberoflayers26.(3Theedgeanddefecteffects:theelectronicdensityofstatescanbestronglyenhancedattheedgescomparedwiththeplaneofgra-phene,witharmchairandzigzagedgesalsohavingdifferentelec-tronicstructure24,27.Inaddition,defects,suchasvacanciesanddislocations,caninduceadditionalelectronicstatesandalsoaffecttheelectrontransferrateingraphene28–30.(4Thecurvatureeffect:graphene,beingonlyoneatomthick,isextremelyflexibleandcanbeeasilybent(intentionallyorunintentionally.Thebentorfoldedgraphenewilldisplaydistinctelectronicstatesfromthoseoftheflatnetworkofgraphene31,32.(5Thedopantandfunctionalgroupeffect:theintroductionofdopantssuchasnitrogen8,33,34,boron35,36,phosphorus37,38,sulfur39,40andevenmetalatoms41–43intothegra-phenematrixcanefficientlytunetheelectronicstatesofthe2Dstructure.Inaddition,themodificationofgraphenewithdifferentfunctionalgroups,suchasthosecontainingoxygen44–46,hydro-gen47andhalogens48,49(F,Cl,Br,I,alsoaffectsitselectronicstates.Anincreaseinthedensityofstates(especiallyaroundtheFermienergyusuallyenhancesthecatalyticactivityofthematerial.Graphenethathasalargenumberofedgesordefects(Fig.1acanbedirectlyusedasacatalyst6,50.Densityfunctionaltheory(DFTcalculationsfromDaiandco-workersindicatedthatthezigzagedgesarechemicallyactive,tendingtoformC–Hbonds51.UsingDFTcalculations,Dengetal.foundthattheoxygenreductionreaction(ORRcanproceedatthezigzagedgesofgra-phenewhereasthearmchairedgesandin-planenetworkofgra-pheneareinactive6.Experimentally,theballmillingmethodwasappliedtocutgrapheneintosmallnanosheetsandincreasethezigzagedgedensity.TheORRactivitycanbesignificantlyincreasedbydecreasingthesizeofthegraphenenanosheets(Fig.2a,b,asthiswillincreasetheratioofedgeatomstobulkatomsinthegra-phenenetwork.Besidestheedgesofgraphene,heteroatomscansubstituteforCatomsofthegraphenematrix(Fig.1b,andthedopantscanactasanelectrondonororacceptordependingontheirelectronegativ-itycomparedwithC.Forexample,theNatompossesseshigherelectronegativitythantheCatom,leadingtoelectrontransferfromCtoNinN-dopedgraphene,whereasinB-dopedgrapheneaBatomhaslowerelectronegativitythanaCatom,resultinginelec-trontransferfromBtoC.Thisdifferencecangeneratetwodifferentactivesites.Inasubstitutivedopingcase,theactivesitesweregen-erallyconsideredtobetheCatomsadjacenttotheN-dopantsintheN-dopedgraphene9,34,whereastheBatomswereconsideredastheactivesitesinB-dopedgraphene38,52.Amongallheteroatom-dopedgraphenestructures,N-dopedgrapheneisthemostintensivelyinvestigatedsystemincatalysis8,9,34,53,54.Forexample,manygroupshaveshownthatN-dopedgraphenecanbeusedasametal-freecatalystfortheORRinH2–O2fuelcells8,34andLi–airbatteries55,56.DFTcalculationsbyYuetal.presenttworeasonsforchangesintheelectronicstructureinN-dopedgraphene9,57.OneisthehigherelectronegativityofNthanC,whichinducespositivechargesonC,andtheotheristheback-donationofthelone-pairelectronsfromNtoC.BotheffectssynergisticallyincreasethedensityofstatesattheFermileveloftheadjacentCatoms,asshowninFig.2d,whichincreasestheirORRactivity.ThereactionenergybarrieroftheORRoccurringattheadjacentCatomsofNatomsisrathermild,andthereforethereactioncanproceedwellwithanassocia-tivemechanismbyafour-electrontransferpathway9.ItshouldbenotedthatdifferentNspeciesandcarbonstructurescanchangetheselectivityofoxygenactivation.Forinstance,severalgroupshaveshownthatN-dopedgrapheneormesoporouscarboncanbeusedforH2O2productionviaatwo-electrontransferpathway58,59.Besidesthis,N-dopedgraphenecanalsobeusedasanefficientcat-alystforselectiveoxidation.Forexample,Gaoetal.andLongetal.reportedindependentlythatN-dopingcanpromotetheselectiveoxidationofethylbenzeneandaromaticalcohol53,60.ApartfromNandBdoping,otherheteroatomssuchasP,SandSehavealsoreceivedgreatinterestingraphene-basedcatalysis37–40,61.Forexam-ple,arecentstudyindicatesthatP-dopedorS-dopedgraphenecanserveasanefficientORRcatalystinalkalineelectrolytes37,39.Besidesnon-metalatoms,metalatomssuchasW,Pt,Co,InandFecanalsobeintroducedintothegraphenematrix41–43.SinglemetalatomsitesembeddedingraphenecanaffecttheelectronicstructureoftheadjacentCatoms,andmoreimportantlytheycanbedirectlyusedasactivesites.DFTcalculationsfromLuetal.62indicatedthatabdefce?e?e?Figure1|Schematicsofcatalysisoractivesitesforvariousgraphenestructuresandtheirheterostructures.a,Activesitesfromdefectsandedges.b,Activesitesfromdopedheteroatoms.c,Activesitesfromfunctionalgroups