• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    GO/MOF復(fù)合材料的制備及其吸附苯和乙醇性能

    2015-10-24 08:01:17劉國(guó)強(qiáng)王明璽黃正宏康飛宇
    新型炭材料 2015年6期
    關(guān)鍵詞:清華大學(xué)教育部石墨

    劉國(guó)強(qiáng),王明璽,黃正宏,康飛宇

    (1.清華大學(xué)材料學(xué)院,先進(jìn)材料教育部重點(diǎn)實(shí)驗(yàn)室,北京100084;2.武漢工程大學(xué)化學(xué)與環(huán)境工程學(xué)院,綠色化工過程教育部重點(diǎn)實(shí)驗(yàn)室,湖北武漢430074;3.清華大學(xué)深圳研究生院,先進(jìn)材料研究所,廣東深圳518055)

    GO/MOF復(fù)合材料的制備及其吸附苯和乙醇性能

    劉國(guó)強(qiáng)1,王明璽2,黃正宏1,康飛宇1

    (1.清華大學(xué)材料學(xué)院,先進(jìn)材料教育部重點(diǎn)實(shí)驗(yàn)室,北京100084;2.武漢工程大學(xué)化學(xué)與環(huán)境工程學(xué)院,綠色化工過程教育部重點(diǎn)實(shí)驗(yàn)室,湖北武漢430074;3.清華大學(xué)深圳研究生院,先進(jìn)材料研究所,廣東深圳518055)

    采用溶劑熱法制備了金屬有機(jī)骨架-氧化石墨烯(MOF/GO)復(fù)合材料,通過氮吸附/脫附、紅外光譜對(duì)其比表面積和孔結(jié)構(gòu)、表面官能團(tuán)進(jìn)行了表征,考察了其吸附苯和乙醇的性能。結(jié)果表明,當(dāng)氧化石墨烯的添加量為5.25 wt%時(shí),復(fù)合材料的比表面積和孔容最大。該材料對(duì)苯和乙醇有很高的吸附容量,其最大吸附容量可分別達(dá)到72和77 cm3/g。MOF-5/GO復(fù)合材料吸附揮發(fā)性有機(jī)物(VOCs)的容量不僅受孔結(jié)構(gòu)的影響,其表面特性也對(duì)吸附性能有重要作用。氧化石墨烯含量為3.5 wt%的GO/MOF復(fù)合材料對(duì)乙醇的吸附容量顯著增強(qiáng)是由于其含有大量的含氧官能團(tuán)。

    金屬有機(jī)骨架化合物(MOF-5);氧化石墨烯(GO);吸附;苯;乙醇

    1 Introduction

    Volatile organic compounds(VOCs)are pollutants present in gas and/or liquid streams of many industrial applications,such as chemical industry(biocides,plastics and solvents),automotive and aerospace industry[1],dry cleaning solvents in the garment industry,and solvent cleaning in the electronic industry.They are very harmful for both human health and environment,even at very low concentrations.It can be remarked that they are:(1)agents that destroy the ozone stratospheric layer,(2)precursors of photochemical oxidants,(3)agents of the acid rain,(4)elements of the climatic change,(5)agents that affect the nervous system and(6)carcinogenic and mutagenic agents[2].Thus,it is important to minimize their use,or to find new materials that can adsorb or mineralize them via environmental friendly catalysts and/or adsorption.

    One of the most useful methods to remove VOCs is the adsorption technique.For adsorption technologies ranging from gas separations to gas storage,selection of the proper solid adsorbents is the key to design an efficient adsorption process.Microporous and mesoporous adsorbents have been frequently used for the removal of VOCs.To examine the practicality of a solid adsorbent,the following characteristics must be considered:porosity,structural stability,reversible uptake and release,and capability for surface modification for creating molecule-specific adsorption sites[3].Removal of VOCs by adsorption process have been performed on several types of adsorbents,which includes carbon materials[4,5],surfactant modified zeolites[6,7],silica aerogels[8],silicalite[9],organic minerals[10],etc.As far as we know,some disadvantages such as low adsorption capacity,flammability and other problems associated with regeneration for most common porous materials are encountered in practical application[11].Therefore,much attention has been paid to new porous materials with a high adsorption capacity.

    Among various adsorbents,metal-organic frameworks(MOFs)are a group of materials,which have had a rapid development and opened new possibilities of applications owing to their excellent properties such as high surface area,high porosity,regular structure,modifiable surfaces and tunable pore size[12,13].In spite of the very high porosities of MOFs,their open framework is not able to provide strong,non-specific adsorption forces to retain small molecules at ambient conditions.Therefore,a surface consisting of a dense arrangement of atoms and a porous network is needed[14].To meet the above requirements,graphite oxide(GO)was selected as another component to prepare GO/MOF nano-composites by Bandosz's group,who also studied the ammonia[15-19],hydrogen sulfide[20]and NO(2)[21]reactive adsorption behavior oftheas-preparedGO/MOFcomposites.There are also many papers on the adsorption of various VOCs on Zn-based metal-organic frameworks MOF-5[22,23].However,as far as we know,there are still few works on the adsorption of VOCs on the GO/MOF-5 composites.

    In the Bandosz's experiments,GO powder prepared by Hummer's method was added in the well-dissolved zinc nitrate/1,4-benzenedicarboxylate(BDC)mixture,and the resulting suspensions were subsequently subjected to the same synthesis procedure as for MOF-5.As an extension of this work,we made some improvement of the synthesis procedure to get GO/MOF-5 composites,and also measured the benzene and ethanol adsorption properties of the samples.

    2 Experimental

    2.1Synthesis of GO/MOF composites

    GO synthesis:GO was prepared from natural graphite powder according to a modified Hummers method[24].46 mL of H2SO4(98%)was placed in a flask immersed into an ice bath.Graphite(2 g)were then added to the flask and stirred vigorously.Next,KMnO4(6 g)was slowly added into the flask,and the reaction temperature was then maintained below 20℃in an ice bath for about 30 min.The flask containing the reaction mixture was then transferred to a water bath at a temperature of 35℃,and the reaction mixture was stirred for about 45 min until a thick paste formed.Water(46 mL)was then added,the reaction temperature was increased to 90℃,and the reaction mixture was stirred for about 30 min.Finally,280 mL water was added into the mixture,followed by a slow addition of 10 mL of 30%aq.H2O2.A yellow dispersion was obtained and washed repeatedly with deionized water to remove the remaining salt until the pH reached about 7,and the solid was then dried under vacuum(50℃)for about 3 days.

    MOFsynthesis:zincnitratehexahydrate(5.2 g)and 1,4-benzenedicarboxylate(1.0 g)were mixed in 35 mL of DMF.The mixture was treated solvothermally at 120℃for 25 hours.The obtained sample was washed with DMF and CHCl3,and MOF was obtained by vacuum drying at 80℃.

    GO/MOF synthesis:GO was dispersed in N,N-dimethylformamide(DMF)to form GO solutions by sonication.The GO/MOF composites were prepared according to the preparation method of MOF-5[15].In a typical reaction,zinc nitrate hexahydrate(5.2 g),BDC(1.0 g)and glucose(0.5 g)were mixed in a 35 mL of GO/DMF solution.The mixture was treated solvothermally at 120℃for 25 hours.The obtained sample was washed with DMF and CHCl3,and MGs were obtained by vacuum drying at 80℃.Samples with GO weight percentages of 1.75%,3.5%,5.25%and 7%were obtained by changing the concentration of the GO in DMF of the solutions,and the samples arereferredtoasMGn(n=1-4),respectively.

    2.2Characterization of materials

    Thenitrogenadsorption-desorptionwasperformed at-196℃using a gas adsorption analyzer(BELsorp-max,Japan).The specific surface area was evaluated using BET method.The Density Functional Theory(DFT)was used to determine the pore size distributions(PSDs).The morphologies of the samples were examined by a LEO 1 530(LEO,Oberkochen,Germany)field emission scanning electron microscope(SEM).Mid-IR spectra(4 000-500 cm-1)were collected on a Nicolet 560 FT-IR spectrometer using pellets with samples dispersed in KBr.X-ray diffraction(XRD)patterns were obtained using a X-ray diffractometer(Rigaku D/max-2500)with Cu-Ka(40 kV,40 kA)radiation.The data were recorded over a 2 range of 5-90°.

    2.3Adsorption of benzene and ethanol

    The adsorption-desorption of benzene and ethanol vapor were measured using a BEL sorp-max at 30℃.All the samples were degassed at 150℃for 12 h prior to the adsorption measurements.The adsorption and desorption time at each p/p0was set at 300 s and the measured p/p0range was from 0 to 0.95.

    3 Results and discussion

    The pore size distributions(PSDs)for various samples evaluated by DFT are shown in Fig.1,the textual parameters are listed in Table 1,and the nitrogen adsorption-desorption isotherms were provided in our previous work[25].All the samples show a significant contribution of ultra-narrow pores of size around W=1 nm in the micropore region,especially for MGG3 with the highest differential pore volume of 2.0 cm3/g.For MG4,some large mesopores appear at 20-30 nm,which is attributed to the“tail”of the isotherms at high relative pressure.

    Fig.1(a),(b)DFT pore size distributions of GO,MGs and MOF-5.

    From Table 1,it can be seen that the surface area of MG1 and MG2 are lower than MOF-5,and it may be related to the blockage of pores by GO with a layer structure,which can be proved by the hysteresis loop H4,a characteristic of slit pores[26].In addition,blockage by carbons derived from partially solvothermal of glucose may be another reason,leading to a dramatically decrease of surface area.Further increase of the GO percentage to 5.25%leads to an increase of surface area,this could be attributed to the formation of graphene reduced by the glucose.The sharply decrease of surface area for MG4 may be attributed to the blockage with the carbonization products derived from hydrothermal of glucose.

    Table1 Textural properties of the samples.

    The FTIR spectra for the samples are shown in Fig.2a.Several bands are observed in the region 1 300-700 cm-1,and they are assigned to the out-ofplane vibrations of BDC.The bands in the region 750-75 cm-1are assigned to aromatic C—H out-ofplane bending vibrations[27],the bands in the 1 000-1 450 cm-1to C—O(hydroxyl,ester,or ether) stretching and O—H bending vibrations[28],the band at 1 390 cm-1to the symmetric stretching of carboxylic groups,those at 1 510 and 1 590 cm-1to the asymmetric stretching of carboxylic groups[16],the broad band at 3 000-700 cm-1to the overlapping bands from O-(hydroxyl or carboxyl),and the bands at 2 855 and 2 922 cm-1to stretching vibrations of aliphaticC—H[15,29].These results indicate that there are a large number of residues including hydroxyl and carboxyl groups on the surface of the as-prepared materials.It also can be seen that with an increase of the GO percentage,the intensity of adsorption bands,representing the amount of functional groups,becomes strong with the GO percentage up to 3.5%and then tends to be weak with a further increasing of the GO percentage.These functional groups can provide a potential avenue to load other functional groups,molecules,ions,and nanoparticles[28].As a result,it may show excellent adsorption performance for gas.

    Fig.2 FT-IR spectra for GO,MOF and MGs(a)before and(b)after adsorption of VOCs.

    Fig.2b shows that the IR spectra of MG2 and MG3 before and after ethanol and benzene vapor adsorption,which exhibits no significant change after the adsorption of benzene vapor.This is attributed to the similar molecular structure of benzene and BDC,which leads to an overlap for their vibration of band.A sharp bands at 3 606 cm-1is observed after ethanol adsorption for both samples,which is the stretching of O—H of gaseous ethanol[30],indicating that the ethanol vapor has been adsorbed onto the composites.

    Fig.3 shows the X-ray diffraction(XRD)patterns of the various samples before and after gas adsorption.The GO spectrum shows a peak at 2θ= 12.1°,indicating an interlayer distance of 0.73 mm.It suggests that the GO has a uniform and enlarged interlayer spacing with the residual oxygenated functional groups on GO sheets[31,32].The MOF-5 diffraction pattern is in good agreement with those found for a well-defined MOF-5 crystal[33].The diffraction patterns of the GO/MOF-5 composites are similar to that observed for MOF-5,which indicates that the MOF-5 structure is preserved.With an increase of the GO percentage,a distortion of the MOF-5 component and the further collapse are observed for the composite materials,and the intensity of diffraction peaks become weaker,especially for MG4,which is attributed to a high content of GO with an amorphous structure,and this result is in good agreement with the SEM observations.After exposure to benzene and ethanol,the patterns are slightly modified,but the overall patterns are preserved.For both of MG2 and MG3,a pronounced splitting appears at 2θ≈9.7°after the adsorption of benzene and ethanol,which indicates that benzene or ethanol retained in the composites leads to a distortion of the structure of the MOF-5 component.This splitting has also been observed by petit et al,who argued that the GO component in the composites induces a distortion of the structure of the MOF-5 component,and the exposure to ammonia can lead to a further distortion.

    Fig.3 X-ray diffraction patterns for the parent and composite materials(a)before and(b)after adsorption of benzene and ethanol.

    The benzene and ethanol adsorption isotherms at 30℃of MGs are shown in Fig.4.It is seen that the benzene uptakes for MG1 and MG2 increase sharply at the initial part,undergoes a long plateau at intermediate relative pressures,and slowly increases at high relative pressures.The adsorption amount follows the order MG3>MG2>MG1>MG4,which is consistent with the surface area.This suggests that the benzene adsorption capacity is related to the textural properties.The steep rise of benzene uptake in low relative pressure region is not observed and the adsorption amount increases slowly with pressure for MG-G1 and MG-G4.The adsorption capacity of MGG4 is much lower than other samples,which may be attributed to the lower surface area and larger pore size.

    Fig.4(a)Benzene and(b)ethanol adsorption-desorption isotherms at 30℃of MGs.

    For each sample,the ethanol adsorption isotherms presented in Fig.4b exhibits the similar trend as the benzene adsorption isotherms.The isotherms of MG2 and MG3 undergo a steep increase at the initial part,nearly plateau at intermediate relative pressures,and a slight rise at high pressures.For MG3,the adsorption amount increases slowly with the relative pressure,which is similar to benzene adsorption behavior.However,the adsorption capacity follows the order MG2>MG3>MG1>MG4,which is different from that of benzene adsorption.Actually,in the entire pressure region,the ethanol uptake of MG2 is higher than that of MG3,following an opposite trend as nitrogen and benzene adsorption.It is known that porous structure and surface chemistry are the two factors affecting the adsorption properties of materials.Since the surface area of MG2 is much lower than MG3,the higher ethanol adsorption capacity for MG2 would be attributed to the much more oxygencontaining functional groups arriving from the glucose modification,which enhances the the interaction of polar ethanol molecular with MG2.

    It is noticeable that the adsorption capacities for MG1 are higher than MG4 for both of benzene and ethanol adsorption,but they are all lower than other samples.This indicates that the porous structure is an important factor for the adsorption of VOCs,and high surface area and pore volume could get high adsorption capacity.Therefore,the adsorption capacities of VOCs for the samples depend on both of the surface chemistry and porous properties.In light of the above findings,the question that remains unanswered is whether the increase in the adsorption of VOCs are related to the surface chemistry or to the high porosity of the composites.Nevertheless,the physical and chemical properties of the VOCs can also have a great influence on the adsorption process.Therefore,additional analysis is required to address these issues.

    4 Conclusions

    GO/MOF composites are synthesized by solvothermal method.Their surface area exhibits a maximum with the GO percentages at 5.25%.The materials exhibit high adsorption capacities for benzene and ethanol,and the maximum uptakes reach up to 72 and 77 cm3/g,respectively.The adsorption capacities of VOCs for the GO/MOF composites are affected by both of the porous structure and surface properties.The ethanol adsorption capacity for the GO/MOF with a GO percentage of 3.5wt%is enhanced by its abundant oxygen-containing functional groups.

    [1]Yamamoto T,Kataoka S,Ohmori T.Characterization of carbon cryogel microspheres as adsorbents for VOC[J].Journal of Hazardous Materials,2010,177(1-3):331-335.

    [2]Lillo-Rodenas M A,Cazorla-Amoros D,Linares-Solano A.Behaviour of activated carbons with different pore size distributions and surface oxygen groups for benzene and toluene adsorption at low concentrations[J].Carbon,2005,43(8):1758-1767.

    [3]Mu B,Walton K S.Adsorption equilibrium of methane and carbon dioxide on porous metal-organic framework Zn-BTB[J].Adsorption-JournaloftheInternationalAdsorptionSociety,2011,17(5):777-782.

    [4]Diaz E,Ordonez S,Vega A.Adsorption of volatile organic compounds onto carbon nanotubes,carbon nanofibers,and high-surface-area graphites[J].Journal of Colloid and Interface Science,2007,305(1):7-16.

    [5]Li L,Liu S,Liu J.Surface modification of coconut shell based activated carbon for the improvement of hydrophobic VOC removal[J].Journal of Hazardous Materials,2011,192(2):683-690.

    [6]Barakat T,Rooke J C,Tidahy H L,et al.Noble-metal-based catalysts supported on zeolites and macro-mesoporous metal oxide supports for the total oxidation of volatile organic compounds [J].Chemsuschem,2011,4(10):1420-1430.

    [7]Silva B,F(xiàn)igueiredo H,Santos V P,et al.Reutilization of Cr-Y zeolite obtained by biosorption in the catalytic oxidation of volatile organic compounds[J].Journal of Hazardous Materials,2011,192(2):545-553.

    [8]Wang D,McLaughlin E,Pfeffer R,et al.Adsorption of organic compounds in vapor,liquid,and aqueous solution phases on hydrophobic aerogels[J].Industrial&Engineering Chemistry Research,2011,50(21):12177-12185.

    [9]Uguina M A,Sotelo J L,Delgado J A,et al.Adsorption of methyl ethyl ketone and trichloroethene from aqueous solutions onto silicalite fixed-bed adsorbers[J].Separation and Purification Technology,2005,42(1):91-99.

    [10]Koh S M,Dixon J B.Preparation and application of organominerals as sorbents of phenol,benzene and toluene[J].Applied Clay Science,2001,18(3-4):111-122.

    [11]Zhao Z,Li X,Li Z.Adsorption equilibrium and kinetics of pxylene on chromium-based metal organic framework MIL-101 [J].Chemical Engineering Journal,2011,173(1):150-157.

    [12]Kitagawa S,Kitaura R,Noro S.Functional porous coordination polymers[J].Angewandte Chemie-International Edition,2004,43(18):2334-2375.

    [13]Furukawa H,Ko N,Go Y B,et al.Ultrahigh porosity in metal-organic frameworks[J].Science,2010,329(5990):424-428.

    [14]Petit C,Bandosz T J.MOF-graphite oxide composites:Combining the uniqueness of graphene layers and metal-organic frameworks[J].Advanced Materials,2009,21(46):4753-4757.

    [15]Petit C,Bandosz T J.MOF-graphite oxide nanocomposites:Surface characterization and evaluation as adsorbents of ammonia [J].Journal of Materials Chemistry,2009,19(36):6521-6528.

    [16]Petit C,Bandosz T J.Enhanced adsorption of ammonia on metal-organic framework/graphite oxide composites:Analysis of surface interactions[J].Advanced Functional Materials,2010,20(1):111-118.

    [17]Petit C,Mendoza B,Bandosz T J.Reactive adsorption of ammonia on Cu-based MOF/graphene composites[J].Langmuir,2010,26(19):15302-15309.

    [18]Petit C,Bandosz T J.Synthesis,characterization,and ammonia adsorption properties of mesoporous metal-organic framework(MIL(Fe))-graphite oxide composites:Exploring the limits of materials fabrication[J].Advanced Functional Materials,2011,21(11):2108-2117.

    [19]Petit C,Huang L,Jagiello J,et al.Toward understanding reactive adsorption of ammonia on cu-MOF/graphite oxide nanocomposites[J].Langmuir,2011,27(21):13043-13051.

    [20]Petit C,Mendoza B,Bandosz T J.Hydrogen sulfide adsorption on MOFs and MOF/graphite oxide composites[J].Chemphyschem,2010,11(17):3678-3684.

    [21]Levasseur B,Petit C,Bandosz T J.Reactive adsorption of NO2on copper-based metal-organic framework and graphite oxide/ metal-organic framework composites[J].ACS Applied Materials &Interfaces,2010,2(12):3606-3613.

    [22]Britt D,Tranchemontagne D,Yaghi O M.Metal-organic frameworks with high capacity and selectivity for harmful gases[J].Proceedings of the National Academy of Sciences of the United States of America,2008,105(33):11623-11627.

    [23]Gu Z-Y,Jiang D-Q,Wang H-F,et al.Adsorption and separation of xylene isomers and ethylbenzene on two Zn-terephthalate metal-organic frameworks[J].Journal of Physical Chemistry C,2010,114(1):311-316.

    [24]Tang Z,Shen S,Zhuang J,et al.Noble-metal-promoted threedimensional macroassembly of single-layered graphene oxide[J].Angewandte Chemie-International Edition,2010,49(27):4603-4607.

    [25]Huang Z-H,Liu G,Kang F.Glucose-promoted Zn-based metal-organic framework/graphene oxide composites for hydrogen sulfide removal[J].Acs Applied Materials&Interfaces,2012,4(9):4942-4947.

    [26]Rouquerol F,Rouquerol J,Sing K.Adsorption by powders and porous solids[J].London:Academic Press,1999:18-20.

    [27]Lua A C,Yang T.Effect of activation temperature on the textural and chemical properties of potassium hydroxide activated carbon prepared from pistachio-nut shell[J].Journal of Colloid and Interface Science,2004,274(2):594-601.

    [28]Zheng M,Liu Y,Jiang K,et al.Alcohol-assisted hydrothermal carbonization to fabricate spheroidal carbons with a tunable shape and aspect ratio[J].Carbon,2010,48(4):1224-1233.

    [29]Sevilla M,F(xiàn)uertes A B.Chemical and structural properties of carbonaceous products obtained by hydrothermal carbonization of saccharides[J].Chemistry-a European Journal,2009,15(16):4195-4203.

    [30]Ellison M D,Morris S T,Sender M R,et al.Infrared and computational studies of the adsorption of methanol and ethanol on single-walled carbon nanotubes[J].Journal of Physical Chemistry C,2007,111(49):18127-18134.

    [31]Seredych M,Tamashausky A V,Bandosz T J.Graphite oxides obtained from porous graphite:The role of surface chemistry and texture in ammonia retention at ambient conditions[J].Advanced Functional Materials,2010,20(10):1670-1679.

    [32]Xu Y,Sheng K,Li C,et al.Self-assembled graphene hydrogel via a one-step hydrothermal process[J].ACS Nano,2010,4(7):4324-4330.

    [33]Hafizovic J,Bjorgen M,Olsbye U,et al.The inconsistency in adsorption properties and powder XRD data of MOF-5 is rationalized by framework interpenetration and the presence of organic and inorganic species in the nanocavities[J].Journal of the A-merican Chemical Society,2007,129(12):3612-3620.

    Preparation of graphene/metal-organic composites and their adsorption performance for benzene and ethanol

    LIU Guo-qiang1,WAN Ming-xi2,HUANG Zheng-hong1,KANG Fei-yu1,3
    (1.Laboratory of Advanced Materials,School of Materials Science and Engineering,Tsinghua University,Beijing100084,China;2.Key Laboratory for Green Chemical Process of Ministry of Education,School of Chemical and Environmental Engineering,Wuhan Institute of Technology,Xiongchu Avenue 693,Wuhan430074,China;3.Institute of Advanced Materials Research,Graduate School at Shenzhen,Tsinghua University,Shenzhen518055,China)

    Graphene/metal-organic composites were synthesized by a solvothermal method and characterized by nitrogen adsorption,SEM and IR and their adsorption properties for benzene and ethanol were investigated.It was found that the surface area and pore volume both have maximum values for a graphene oxide(GO)percentage of 5.25 wt%.The composites have high adsorption capacities for both benzene and ethanol,and the maximum uptakes reach 72 and 77 cm3/g,respectively.The adsorption capacities of volatile organic compounds are determined by both the pore structure and the surface properties.The maximum ethanol adsorption capacity for the composite with a GO percentage of 3.5 wt%is due to its abundant oxygen-containing functional groups.

    MOF-5;Graphene;Adsorption;Benzene;Ethanol

    date:2015-10-26;Revised date:2015-12-08

    National High Technology Research and Development Program of China(2010AA064907).

    HUANG Zheng-hong,Ph.D,Associate Professor.E-mail:zhhuang@mail.tsinghua.edu.cn English edition available online ScienceDirect(http://www.sciencedirect.com/science/journal/18725805).

    TQ127.1+1

    A

    國(guó)家高技術(shù)研究發(fā)展計(jì)劃(2010AA064907).

    黃正宏,博士,副研究員.E-mail:zhhuang@mail.tsinghua.edu.cn

    1007-8827(2015)06-0566-06

    10.1016/S1872-5805(15)60205-0

    猜你喜歡
    清華大學(xué)教育部石墨
    清華大學(xué):“如鹽在水”開展課程思政
    石墨系升溫球的實(shí)踐與應(yīng)用
    昆鋼科技(2022年1期)2022-04-19 11:36:14
    我的清華大學(xué)自主招生經(jīng)歷
    石墨烯的健康路
    教育部召開座談會(huì)推進(jìn)一流大學(xué)和一流學(xué)科建設(shè)
    新課程研究(2016年1期)2016-12-01 05:52:14
    他永遠(yuǎn)是我們的老學(xué)長(zhǎng)——清華大學(xué)受助研究生來信摘編
    教育部:高考地方性加分項(xiàng)目2018年減至35個(gè)
    我校兩教育部重大課題攻關(guān)項(xiàng)目開題
    石墨礦中固定碳的分析與探討
    一道2009年清華大學(xué)自主招生數(shù)學(xué)試題的思考
    观看免费一级毛片| 国产欧美日韩精品亚洲av| 免费观看在线日韩| 日韩欧美在线二视频| 亚洲国产色片| 天天躁日日操中文字幕| 少妇丰满av| 熟女电影av网| 中文在线观看免费www的网站| 亚洲精品影视一区二区三区av| 日韩欧美一区二区三区在线观看| 12—13女人毛片做爰片一| 日日摸夜夜添夜夜添小说| 女人被狂操c到高潮| 久久亚洲真实| 欧美bdsm另类| 免费av不卡在线播放| 日本一二三区视频观看| 亚洲综合色惰| 精品一区二区三区人妻视频| 亚洲在线观看片| 男人和女人高潮做爰伦理| 一个人免费在线观看电影| 国产不卡一卡二| 亚洲经典国产精华液单| 欧洲精品卡2卡3卡4卡5卡区| 99riav亚洲国产免费| 深夜精品福利| 精华霜和精华液先用哪个| 三级男女做爰猛烈吃奶摸视频| 亚洲欧美日韩高清在线视频| 日韩 亚洲 欧美在线| 久久久成人免费电影| 成年女人看的毛片在线观看| 黄色欧美视频在线观看| 日本欧美国产在线视频| 久久这里只有精品中国| 精品一区二区三区视频在线观看免费| 啦啦啦韩国在线观看视频| 亚洲一区高清亚洲精品| 午夜激情福利司机影院| 国产精品精品国产色婷婷| 日韩欧美三级三区| 夜夜看夜夜爽夜夜摸| 干丝袜人妻中文字幕| 亚洲av第一区精品v没综合| 国产主播在线观看一区二区| 亚洲中文日韩欧美视频| 蜜桃久久精品国产亚洲av| 日韩欧美精品免费久久| 一进一出好大好爽视频| av天堂中文字幕网| av专区在线播放| 久久草成人影院| 亚洲欧美日韩高清专用| 日韩av在线大香蕉| 亚洲内射少妇av| 久久精品久久久久久噜噜老黄 | 亚洲精品乱码久久久v下载方式| 一区二区三区四区激情视频 | 午夜福利视频1000在线观看| 综合色av麻豆| 少妇丰满av| 久久热精品热| 成年版毛片免费区| 亚洲在线自拍视频| 欧美极品一区二区三区四区| 毛片一级片免费看久久久久 | 国产精品国产三级国产av玫瑰| 久久精品91蜜桃| 老司机深夜福利视频在线观看| 九色国产91popny在线| 国产一区二区三区视频了| 国产大屁股一区二区在线视频| 欧美xxxx性猛交bbbb| 搡老妇女老女人老熟妇| 少妇丰满av| 日本免费一区二区三区高清不卡| 网址你懂的国产日韩在线| 亚洲中文日韩欧美视频| 国产久久久一区二区三区| 亚洲一区高清亚洲精品| 日本撒尿小便嘘嘘汇集6| 听说在线观看完整版免费高清| 亚洲欧美日韩无卡精品| 亚洲人成网站在线播放欧美日韩| 99久久精品一区二区三区| 老司机午夜福利在线观看视频| 麻豆成人午夜福利视频| 中文字幕熟女人妻在线| 久久久成人免费电影| 一区福利在线观看| 天天一区二区日本电影三级| 欧美潮喷喷水| 亚洲成人久久爱视频| 我要搜黄色片| 有码 亚洲区| 国产91精品成人一区二区三区| 亚洲乱码一区二区免费版| 动漫黄色视频在线观看| 婷婷亚洲欧美| 国产在线男女| 欧美最黄视频在线播放免费| 国产色爽女视频免费观看| 99精品久久久久人妻精品| 中亚洲国语对白在线视频| 女生性感内裤真人,穿戴方法视频| 久久久久久国产a免费观看| 国产精品女同一区二区软件 | 国产日本99.免费观看| 国产真实乱freesex| 日本 欧美在线| 日本爱情动作片www.在线观看 | 精品久久久久久久久av| 色噜噜av男人的天堂激情| 大型黄色视频在线免费观看| 精品人妻1区二区| 五月伊人婷婷丁香| 国产视频一区二区在线看| 尾随美女入室| 亚洲国产精品久久男人天堂| 一级黄片播放器| 91精品国产九色| 色视频www国产| 九九爱精品视频在线观看| 18禁黄网站禁片午夜丰满| www.www免费av| 在线观看午夜福利视频| 久久国内精品自在自线图片| videossex国产| 麻豆成人午夜福利视频| 国产人妻一区二区三区在| 国产精品久久视频播放| 露出奶头的视频| 国产91精品成人一区二区三区| АⅤ资源中文在线天堂| 色哟哟·www| 少妇裸体淫交视频免费看高清| 亚洲av日韩精品久久久久久密| 亚洲性夜色夜夜综合| 十八禁网站免费在线| 亚洲精品色激情综合| 美女免费视频网站| 亚洲国产高清在线一区二区三| 亚洲专区国产一区二区| 久久精品国产亚洲av涩爱 | 两个人的视频大全免费| 国产午夜福利久久久久久| 亚洲精品在线观看二区| 99久久久亚洲精品蜜臀av| 1000部很黄的大片| 国产视频一区二区在线看| 赤兔流量卡办理| 亚洲天堂国产精品一区在线| 美女被艹到高潮喷水动态| 免费观看精品视频网站| 国产探花在线观看一区二区| 尤物成人国产欧美一区二区三区| 久久人妻av系列| 国产在线精品亚洲第一网站| 免费看日本二区| 国产v大片淫在线免费观看| 成人综合一区亚洲| 国产日本99.免费观看| 少妇人妻精品综合一区二区 | 在线免费观看不下载黄p国产 | 人妻制服诱惑在线中文字幕| 天天一区二区日本电影三级| 欧美激情国产日韩精品一区| 在线国产一区二区在线| 欧美最黄视频在线播放免费| 精品一区二区三区av网在线观看| 日本一本二区三区精品| 亚洲在线自拍视频| 人人妻人人看人人澡| 小蜜桃在线观看免费完整版高清| 国产精品电影一区二区三区| av在线亚洲专区| 国产精品98久久久久久宅男小说| 亚洲av二区三区四区| 免费av不卡在线播放| 黄色日韩在线| 欧美激情国产日韩精品一区| 久久久精品大字幕| 窝窝影院91人妻| 尾随美女入室| 伦理电影大哥的女人| 精品不卡国产一区二区三区| 动漫黄色视频在线观看| 九九在线视频观看精品| 99视频精品全部免费 在线| 国产白丝娇喘喷水9色精品| 国产午夜精品论理片| 中文字幕av在线有码专区| 联通29元200g的流量卡| 午夜免费男女啪啪视频观看 | 91麻豆av在线| 精品久久久久久成人av| 亚洲人成网站在线播| 国产久久久一区二区三区| 乱码一卡2卡4卡精品| 日韩大尺度精品在线看网址| 午夜视频国产福利| 亚洲,欧美,日韩| 国产精品亚洲美女久久久| 伦精品一区二区三区| h日本视频在线播放| 亚洲一区二区三区色噜噜| 日韩欧美国产一区二区入口| 少妇丰满av| 亚洲性夜色夜夜综合| 日韩强制内射视频| 欧美成人a在线观看| 成人无遮挡网站| 久久久国产成人免费| 麻豆国产av国片精品| 韩国av在线不卡| 级片在线观看| 观看免费一级毛片| 国内久久婷婷六月综合欲色啪| 99精品在免费线老司机午夜| 欧美日本视频| 国产老妇女一区| 国内少妇人妻偷人精品xxx网站| 免费看a级黄色片| 黄片wwwwww| 国产精品国产三级国产av玫瑰| 天堂动漫精品| 亚洲av第一区精品v没综合| 日本 欧美在线| 能在线免费观看的黄片| 两人在一起打扑克的视频| 亚洲美女搞黄在线观看 | 久久久久国内视频| 午夜精品在线福利| 干丝袜人妻中文字幕| 别揉我奶头 嗯啊视频| 成人综合一区亚洲| 日日摸夜夜添夜夜添av毛片 | 国产私拍福利视频在线观看| 黄片wwwwww| 国产av不卡久久| 免费人成视频x8x8入口观看| 国内精品宾馆在线| 桃色一区二区三区在线观看| 最近最新中文字幕大全电影3| 亚洲av五月六月丁香网| 热99在线观看视频| 极品教师在线免费播放| 两人在一起打扑克的视频| 色综合婷婷激情| 老熟妇仑乱视频hdxx| 天堂动漫精品| 性插视频无遮挡在线免费观看| 蜜桃亚洲精品一区二区三区| 99久久精品一区二区三区| 小说图片视频综合网站| 五月伊人婷婷丁香| 最近视频中文字幕2019在线8| 毛片女人毛片| 久久精品国产亚洲av天美| 中国美白少妇内射xxxbb| 欧美+亚洲+日韩+国产| 国产一区二区三区在线臀色熟女| 国产麻豆成人av免费视频| 大型黄色视频在线免费观看| 国产成年人精品一区二区| 国国产精品蜜臀av免费| 亚洲四区av| 大又大粗又爽又黄少妇毛片口| 亚洲中文字幕一区二区三区有码在线看| 国产不卡一卡二| 18禁在线播放成人免费| 美女高潮的动态| 人人妻人人看人人澡| 色哟哟哟哟哟哟| 五月玫瑰六月丁香| 欧美黑人巨大hd| 精品日产1卡2卡| 在线播放无遮挡| 国产乱人视频| 免费高清视频大片| 久久天躁狠狠躁夜夜2o2o| 欧美3d第一页| 久久久久久久久中文| 91久久精品电影网| 国产高清视频在线观看网站| 成年人黄色毛片网站| 亚洲久久久久久中文字幕| 国产精品一区二区三区四区免费观看 | 亚洲aⅴ乱码一区二区在线播放| 国产欧美日韩一区二区精品| 人妻久久中文字幕网| 久久久久久久久中文| 亚洲经典国产精华液单| 日韩精品青青久久久久久| 久久人人爽人人爽人人片va| 成人无遮挡网站| 91精品国产九色| 91狼人影院| 日本-黄色视频高清免费观看| 日韩欧美三级三区| 男女之事视频高清在线观看| x7x7x7水蜜桃| 亚洲午夜理论影院| 婷婷精品国产亚洲av| 嫩草影视91久久| 亚洲一级一片aⅴ在线观看| 少妇的逼好多水| 日本 欧美在线| 国产亚洲欧美98| 人妻丰满熟妇av一区二区三区| 欧美三级亚洲精品| 亚洲精品色激情综合| 中国美女看黄片| 成人亚洲精品av一区二区| 国产午夜精品论理片| 欧美+亚洲+日韩+国产| 亚洲国产欧洲综合997久久,| 校园人妻丝袜中文字幕| 男人狂女人下面高潮的视频| 欧美日本视频| 欧美不卡视频在线免费观看| 国产爱豆传媒在线观看| 欧美日韩精品成人综合77777| 色综合站精品国产| 99riav亚洲国产免费| 别揉我奶头 嗯啊视频| 99久久九九国产精品国产免费| 欧美日本亚洲视频在线播放| 欧美性感艳星| 美女高潮的动态| 国产伦在线观看视频一区| 久久久午夜欧美精品| 91久久精品国产一区二区三区| 精品人妻熟女av久视频| 精品国内亚洲2022精品成人| 麻豆久久精品国产亚洲av| 国产成人福利小说| 欧美成人一区二区免费高清观看| 欧美极品一区二区三区四区| 亚洲,欧美,日韩| 日韩欧美精品v在线| 免费大片18禁| 美女cb高潮喷水在线观看| 亚洲图色成人| 国产精品不卡视频一区二区| 又紧又爽又黄一区二区| 国产主播在线观看一区二区| 免费大片18禁| 精品99又大又爽又粗少妇毛片 | 日本与韩国留学比较| 观看美女的网站| 亚洲成a人片在线一区二区| 看黄色毛片网站| 亚洲真实伦在线观看| 色综合站精品国产| 看片在线看免费视频| 婷婷丁香在线五月| 国产探花在线观看一区二区| 免费在线观看影片大全网站| 久久久久久国产a免费观看| 国产精品美女特级片免费视频播放器| 可以在线观看毛片的网站| 亚洲电影在线观看av| 日韩欧美三级三区| 毛片女人毛片| 久久久久久久久中文| 国产三级中文精品| 亚洲内射少妇av| 男人和女人高潮做爰伦理| 亚洲第一电影网av| 国产精品亚洲美女久久久| 国产国拍精品亚洲av在线观看| 在线观看舔阴道视频| 欧美人与善性xxx| 国产精品98久久久久久宅男小说| 日本成人三级电影网站| 亚洲成人精品中文字幕电影| av在线天堂中文字幕| bbb黄色大片| 成人精品一区二区免费| 不卡一级毛片| 99久久中文字幕三级久久日本| 性插视频无遮挡在线免费观看| 男人狂女人下面高潮的视频| 又黄又爽又免费观看的视频| 午夜福利18| 一区二区三区四区激情视频 | 久久久午夜欧美精品| a级毛片a级免费在线| 免费在线观看成人毛片| 日日摸夜夜添夜夜添av毛片 | 国产精品嫩草影院av在线观看 | 身体一侧抽搐| 国产av不卡久久| 国产精品美女特级片免费视频播放器| 在线观看舔阴道视频| 国产精品一区二区三区四区免费观看 | 日日干狠狠操夜夜爽| 一卡2卡三卡四卡精品乱码亚洲| 欧美日韩瑟瑟在线播放| 国产三级在线视频| 亚洲精品国产成人久久av| 午夜激情欧美在线| 尾随美女入室| 日本色播在线视频| videossex国产| 精品人妻一区二区三区麻豆 | 国产成人a区在线观看| 国产精品一区二区性色av| 露出奶头的视频| 亚洲美女搞黄在线观看 | 在线观看66精品国产| 国产国拍精品亚洲av在线观看| 日韩欧美在线二视频| 亚洲中文字幕日韩| 长腿黑丝高跟| 给我免费播放毛片高清在线观看| 久久久久久久亚洲中文字幕| 午夜福利高清视频| 午夜亚洲福利在线播放| 色尼玛亚洲综合影院| 欧美三级亚洲精品| 欧美日韩中文字幕国产精品一区二区三区| 久久草成人影院| 免费观看在线日韩| 成年女人永久免费观看视频| 两人在一起打扑克的视频| 国产精品一区二区三区四区免费观看 | 国产精品野战在线观看| 亚洲精品在线观看二区| 国产精品久久久久久av不卡| 直男gayav资源| 国产高清视频在线播放一区| 制服丝袜大香蕉在线| 99久国产av精品| av天堂中文字幕网| 琪琪午夜伦伦电影理论片6080| 婷婷丁香在线五月| 一个人看的www免费观看视频| 亚洲国产欧洲综合997久久,| 少妇人妻精品综合一区二区 | 18禁黄网站禁片免费观看直播| 18禁裸乳无遮挡免费网站照片| 成人一区二区视频在线观看| 亚洲精品一区av在线观看| 欧美成人一区二区免费高清观看| 国产色爽女视频免费观看| 日本免费一区二区三区高清不卡| 女人十人毛片免费观看3o分钟| 亚洲天堂国产精品一区在线| 欧美bdsm另类| 欧美色欧美亚洲另类二区| 日本免费一区二区三区高清不卡| 国产精品三级大全| 国产精品女同一区二区软件 | 午夜福利在线在线| 日韩av在线大香蕉| 在线观看舔阴道视频| 国产蜜桃级精品一区二区三区| 麻豆国产av国片精品| 中文资源天堂在线| 久久久久久伊人网av| 午夜精品久久久久久毛片777| 伊人久久精品亚洲午夜| 欧美日韩中文字幕国产精品一区二区三区| 乱码一卡2卡4卡精品| 午夜福利高清视频| 欧美zozozo另类| 国产精品野战在线观看| 99久久精品热视频| 99精品久久久久人妻精品| 国产伦在线观看视频一区| 99在线人妻在线中文字幕| 天堂影院成人在线观看| 午夜福利在线在线| 一个人观看的视频www高清免费观看| 国产aⅴ精品一区二区三区波| 亚洲精品亚洲一区二区| 一个人免费在线观看电影| 啦啦啦韩国在线观看视频| 97超视频在线观看视频| 人妻少妇偷人精品九色| 成人国产综合亚洲| 国国产精品蜜臀av免费| 久久精品国产亚洲av天美| 国产三级在线视频| 亚洲欧美日韩高清专用| 亚洲av五月六月丁香网| 露出奶头的视频| 国产成人a区在线观看| 色噜噜av男人的天堂激情| 精品一区二区三区视频在线| 免费无遮挡裸体视频| 露出奶头的视频| av在线老鸭窝| 亚洲精品成人久久久久久| aaaaa片日本免费| 精品一区二区三区人妻视频| 亚洲黑人精品在线| 老女人水多毛片| 日本与韩国留学比较| 日韩欧美精品免费久久| av在线亚洲专区| 国国产精品蜜臀av免费| 黄色丝袜av网址大全| 国产男靠女视频免费网站| aaaaa片日本免费| 日韩欧美国产一区二区入口| 亚洲国产色片| 日本黄色视频三级网站网址| 亚洲五月天丁香| 国产伦一二天堂av在线观看| 亚洲熟妇中文字幕五十中出| 欧洲精品卡2卡3卡4卡5卡区| 午夜福利在线在线| 最近在线观看免费完整版| 在线a可以看的网站| 一夜夜www| 国产av麻豆久久久久久久| 丰满人妻一区二区三区视频av| 欧美高清性xxxxhd video| 午夜影院日韩av| 麻豆成人午夜福利视频| 国产精品亚洲一级av第二区| 亚洲av熟女| 伊人久久精品亚洲午夜| 我要搜黄色片| 亚洲,欧美,日韩| 欧美一区二区亚洲| 国产综合懂色| 日本与韩国留学比较| 夜夜夜夜夜久久久久| 小说图片视频综合网站| 露出奶头的视频| 欧美日本视频| 亚洲av免费在线观看| 欧美中文日本在线观看视频| 午夜免费成人在线视频| 春色校园在线视频观看| 国产精品亚洲美女久久久| 亚洲性夜色夜夜综合| 亚洲av成人精品一区久久| 亚洲自拍偷在线| 亚洲成a人片在线一区二区| 国产精品综合久久久久久久免费| 午夜爱爱视频在线播放| 国产一区二区三区视频了| 亚洲欧美清纯卡通| 国产午夜福利久久久久久| 亚洲国产色片| 小说图片视频综合网站| 精品久久久久久久末码| 91狼人影院| 国产欧美日韩精品亚洲av| 又爽又黄a免费视频| 精品人妻视频免费看| 成年免费大片在线观看| 日韩欧美精品v在线| 亚洲一区高清亚洲精品| av在线观看视频网站免费| 日本黄色片子视频| 人人妻人人澡欧美一区二区| 成年免费大片在线观看| 日本五十路高清| 国产视频内射| 国产男靠女视频免费网站| 韩国av在线不卡| 日韩精品青青久久久久久| 一级黄片播放器| 亚洲精品亚洲一区二区| 午夜激情福利司机影院| 久久精品人妻少妇| x7x7x7水蜜桃| 日韩一本色道免费dvd| 可以在线观看的亚洲视频| 99久久久亚洲精品蜜臀av| 精品欧美国产一区二区三| 成年女人看的毛片在线观看| 国产精华一区二区三区| 国产一区二区三区视频了| 可以在线观看的亚洲视频| 久久精品人妻少妇| 亚洲人成伊人成综合网2020| 波多野结衣高清无吗| 久久草成人影院| 成人国产麻豆网| 国产久久久一区二区三区| 久久精品夜夜夜夜夜久久蜜豆| 欧美成人免费av一区二区三区| 午夜福利18| 国产精品久久久久久久久免| 亚洲欧美日韩无卡精品| 欧美成人免费av一区二区三区| 少妇丰满av| 亚洲国产精品久久男人天堂| 九九久久精品国产亚洲av麻豆| 在线播放国产精品三级| 亚州av有码| 午夜精品一区二区三区免费看| 免费不卡的大黄色大毛片视频在线观看 | 亚洲av中文字字幕乱码综合| 久久久精品欧美日韩精品| 日日摸夜夜添夜夜添av毛片 | 91狼人影院| 亚洲av熟女| 国内精品美女久久久久久| 两人在一起打扑克的视频| 婷婷色综合大香蕉| 欧美高清性xxxxhd video| 一进一出好大好爽视频| 日本一本二区三区精品| 国产黄a三级三级三级人| 国产精品人妻久久久久久|