快速热解法制备炭包覆纳米金属磁性颗粒
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第25卷第3期 2010年6月 新型炭
NEW CARB0N 材料 MATERIALS Vo1.25 No.3 Jun.2010
Article ID: 1007—8827(2010)03—0199436
Preparation of carbon・encapsulated metal magnetic nanoparticles by an instant pyrolysis method MA Chen ,LUO Bin ,SONG Huai—he ,ZHI Lin-jie (1.State Key Laboratory of Chemical Resource Engineering,Beijing University of Chemical Technology,Beijing 100029,China; 2.National Centerfor Nanoscience and Technology of China,Being 100190,China)
Abstract: Carbon—encapsulated iron and nickel magnetic nanoparticles(CEMNPs)were synthesized from their salt precursors using an instant pyrolysis method.The morphologies,structural features and magnetic properties of the patti— cles were investigated by transmission electron microscopy,X—ray diffraction,simultaneous thermogravimetry—differential scanning calorimetry and vibrating sample magnetometry.It was found that almost al1 of the CEMNPs were spherica1. and their size changed from 10 to 30 nm,whereas the size of the carbon—encapsulated iron nanoparticles changed from 50 to 60 nm.The magnetic properties of the products indicated that the carbon—encapsulated iron nanoparticles were para— magnetic and their properties were tunable with the iron content.The present approach is promising for large—scale pro— duction Of CEMNPs. Keywords: Nanomaterials;Carbon encapsulation;Magnetic nanoparticles;Instant pyrolysis CLC number:TB 333 D ument code: A
1 Introduction Magnetic nanoparticles have attracted significant academic and technological attention because of their unique physical properties and potential applications in magnetic recording ,environmental protection , biomedicine ~,magnetic resonance imaging as con— trast agents ,field—oriented drug delivery sys— temsl .biotoxin scavengerslo J.as well as the mag—
netic fluid hyperthermia .Recently,ferromagnetic transition metal nanoparticles have boosted intensive research work because of their excellent magnetic properties(the saturation magnetization of Fe nano— particles is twice that of magnetite,which is a very popular magnetic materia1). However,the use of pure metal magnetic nano— particles such as iron(Fe),nickel(Ni),and cobalt (Co)is difficult because of their inherent instabilities such as oxidation in air。dissolution in acid,and easy agglomeration,which limits their potential applica— tions in industry or scientitic studies.To overcome these limitations,depositing a protective shell has been recommended as one prospective method to im— prove the chemical stability of metal nanoparticles. By far,various coating materials have been proposed, e.g.,metal oxides ,silica[ ,titanium ,boron oxide[….and polymers E .Carbon seems to be the most desired material for encapsulation,because such coatings possess several advantages:(1)high stabili— ty in both chemical and physical environments that ef- fectively prevent the agglomeration and oxidation of nanoparticles 13l and(2)good biocompatibility and high surface activity[14]. Solution phase chemical reduction[15]。arc dis— charge 1I6_,microwave heating[17],radio frequency thermal plasma[18],explosionlI 9l,co—pyrolysis ¨, and chemical vapor condensation 22 have been印一 plied to synthesize carbon・-encapsulated metal magnet-- ic nanoparticles(CEMNPs).However.most of these methods require relatively harsh reaction conditions that typically lead to operational complexity,high cost,or dificulties in terms of practical applications. In addition,byproducts such as carbon nanotubes, nanofibers,nanoparticles,and free amorphous carbon are likely to form by using these techniques.More・ over,the carbon coatings on CEMNPs produced by these methods often do not clearly show a graphitic structure that is expected to protect effectively the meta1 c0res[2 . Therefore,a more efficient and lower cost tech— nique to coat metal nanoparticles with a graphitic
Received date:2009 -25: Revised date:2010436 1 Corresponding authors:ZHI Lin-jie.E—mail:zhilj@nanoctr.cn;SONG Huai-he.E—mail:songhh@mail.buct.edu.cn Author introduction:MA Chen(1 984一),female,Postgraduate Student,working on carbonaceous nanomaterials and their applications E—mail:machen0129@yahoo.co English edition available online ScienceDirect(http://www.sciencedirect.com/science/joumal/18725805). DOI:10.1016/Sl872.5805(09)60028-7