CAJ | 학술논문

为了了解不同粒径的柴油机排放颗粒物中石墨烯结构，利用激光拉曼光谱仪和软X射线谱学显微光束线站分析了不同粒径的柴油机排放颗粒物中石墨烯结构和碳原子价态信息。结果表明，排放颗粒的D1峰（由无序石墨烯边缘和基底碳原子的A1g对称振动而产生的）与D2峰（无序石墨烯表面碳原子的E2g对称振动）的相对强度在3.34～4.01之间，石墨烯缺陷类型主要为边缘缺陷。随着排放颗粒粒径的增加，D1峰的半高宽分别增加了2.8和6.7 cm-1，化学异相性增加；D1峰与G峰（是理想石墨烯晶格E2g对称振动引起的）的相对强度分别降低了14.67%和27.17%，石墨化程度提高；D3峰（代表排放颗粒中的无定形碳，主要包括有机成分、碎片和官能团）的相对强度R3分别降低了13.73%和39.22%，无定形碳含量降低。石墨烯晶格内部C-C键长与粒径关系不大，晶格内部C-C键长约为0.142 nm；随着排放颗粒粒径的增加，石墨烯微晶尺寸分别增加了约0.412和0.821 nm，相邻石墨烯间距降低，排放颗粒活性增加；脂肪族C=C化学键、脂肪族C-H和羧基C=O化学键含量降低，“石墨烯性”C=C、酚类C-OH和酮类C=O化学键含量增加。该研究可为不同粒径柴油机排放颗粒形成机理的完善和排放颗粒净化装置的优化提供参考。
위료료해불동립경적시유궤배방과립물중석묵희결구，이용격광랍만광보의화연X사선보학현미광속선참분석료불동립경적시유궤배방과립물중석묵희결구화탄원자개태신식。결과표명，배방과립적D1봉（유무서석묵희변연화기저탄원자적A1g대칭진동이산생적）여D2봉（무서석묵희표면탄원자적E2g대칭진동）적상대강도재3.34～4.01지간，석묵희결함류형주요위변연결함。수착배방과립립경적증가，D1봉적반고관분별증가료2.8화6.7 cm-1，화학이상성증가；D1봉여G봉（시이상석묵희정격E2g대칭진동인기적）적상대강도분별강저료14.67%화27.17%，석묵화정도제고；D3봉（대표배방과립중적무정형탄，주요포괄유궤성분、쇄편화관능단）적상대강도R3분별강저료13.73%화39.22%，무정형탄함량강저。석묵희정격내부C-C건장여립경관계불대，정격내부C-C건장약위0.142 nm；수착배방과립립경적증가，석묵희미정척촌분별증가료약0.412화0.821 nm，상린석묵희간거강저，배방과립활성증가；지방족C=C화학건、지방족C-H화최기C=O화학건함량강저，“석묵희성”C=C、분류C-OH화동류C=O화학건함량증가。해연구가위불동립경시유궤배방과립형성궤리적완선화배방과립정화장치적우화제공삼고。
Particulate matter emitted from diesel engine is a factor that makes PM2.5 (particulate matter with a diameter of lower than 2.5μm) increase, which is related to several adverse health effects including respiratory tract inflammation and cancer. Particulate matter is classified to 3 size modes, i.e. the nucleation mode (<50 nm), the accumulation mode (100-1 000 nm) and the coarse mode (>1 000 nm). As is known to all, particulate matter with smaller size does more harm to human than particulate matter with larger size. It is very necessary to carry out research on reducing particulate matter emitted from diesel engine, especially particulate matter with smaller size. It has been demonstrated that there is graphene structure in particulate matter emitted from diesel engine and graphene structure is related to particulate matter removal. Micro-orifice uniform deposition impactor which was produced in MSP company in America was used to collect diesel particulate matter with 3 size ranges, which were 0.18-0.32μm, >0.32-0.56μm and >0.56-1μm respectively. Raman spectroscopy, a fast and nondestructive method, was used to test crystal structure of carbon material. Near edge X-ray absorption spectra, a nondestructive method, was adopted to characterize molecular structure and valence state of carbon atom by using synchrotron radiation technique. DXR Raman spectrometer and soft X-ray microscopy beamline station were used to analyze the defect type of graphene structure, degree of graphitization, crystallite size of graphene, neighboring graphene spacing, molecular structure and valence state of carbon atom. The results showed that the ratio of D1 peak to D2 peak ranged from 3.34 to 4.01, which indicated that the defect type of graphene structure in diesel particulate matter mainly was graphene edge defect. With the size of particulate matter decreasing, the proportion of graphene edge defect increased. When the size of particulate matter increased, width at half maximum of D1 peak increased by 2.8 and 6.7 cm-1, indicating that the material type in particulate matter increased and the chemical heterogeneity of particulate matter was higher. The ratio of D1 peak to G peak decreased by 14.67% and 27.17% respectively with particulate matter changing from small size to the other 2 bigger sizes, which indicated that the proportion of order graphene in diesel particulate matter increased and led to higher graphitic-like structure and degree of graphitization. When the size of particulate matter increased, the relative intensity of D3 peakdecreased by 13.73% and 39.22%, respectively. That was to say the proportion of amorphous carbon especially organic ingredients reduced. The length of C-C bond in graphene lattice had no relationship with the size of diesel particulate matter. The length of C-C bond in graphene lattice of diesel particulate matter with 3 size ranges was about 0.142 nm. When the size of particulate matter increased, the crystallite size of graphene increased and the neighboring graphene spacing decreased, which indicated the oxidative reactivity of particulate matter reduced and the energy in the process of oxidizing diesel particulate matter increased. The types of surface functional groups in particulate matter had no relationship with the size of diesel particulate matter. There were many types of surface functional groups which were “graphene” C=C, C=C, aliphatic C=C, phenolic C-OH, ketones C=O, aliphatic C-H and carboxy C=O respectively. With the size of particulate matter increasing, aliphatic C=C, aliphatic C-H, carboxy C=O in diesel particulate matter decreased and “graphite” C=C, phenolic C-OH, ketones C=O in diesel particulate matter increased. This study can provide reference for the perfection of the formation mechanism of diesel particulate matter with different size range and for the optimization of particulate matter removal device.