• <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 ?

    有機相化學鍍鋁法制備Al/石墨烯復合材料粉末

    2019-05-07 07:28:12徐明英高建峰白培康
    無機化學學報 2019年5期
    關(guān)鍵詞:鍍鋁中北大學理學院

    段 政 徐明英 高建峰*, 郝 敏 劉 艷 馬 潔 白培康

    (1中北大學理學院,太原 030051)

    (2中北大學材料科學與工程學院,太原 030051)

    0 Introduction

    In recent years,graphene has been a promising application prospect in the field of composite materials due to its excellent mechanical/functional properties and its unique physical/chemical properties[1-2].Compared with graphene reinforced polymer matrix composites[1],graphene reinforced metal matrix composites(GNP-MMC),especially graphene reinforced aluminum matrix composites (Gr/Al),have not been studied in depth.The special atomic structure and properties of graphene make it an excellent additive for the preparation of reinforced and toughened composites.As distinct from other carbon allotropes such as carbon nanotubes (CNTs)and graphite,graphene has the characteristic 2D structure,which makes its specific surface area larger than those of CNTs or graphite[3],thus providing more area to interact with the matrix material.Therefore,graphene is an ideal reinforcement for the preparation of high-performance composites of any kind of matrix(whether polymer[4-6],ceramic[7-8],or metal[9-11]),and is expected to improve the mechanical and thermal properties of the aluminum matrix greatly when added to the aluminum matrix.

    At present,the methods for preparing Gr/Al are casting[12-14],ball-milling[15-17],powder metallurgy[18]and friction stir processing (FSP)[19].The nanosized(or microsized)Gr/Al can be prepared by casting and ball-milling methods;GNP-MMC prepared by powder metallurgy technology have good physical and chemical properties;Gr/Al prepared by the FSP method hasfew impurities.However,theabove methods have a common problem that the complicated structure Gr/Al prepared by the above methods is longtime,high cost and even difficult to form the shape;moreover,the graphene is easily agglomerated in the matrix and has poor bonding property with the matrix interface.Thiscannotmeetthe material requirements of selective laser melting (SLM).The metal powder for SLM forming need high purity,good sphericity,small particle size and narrow particle size distribution (15 ~45 μm).Metal powder properties directly affect the stability of the SLM-forming process and the structural properties of the part.Because of the large difference in density between graphene and the aluminum matrix,poor wettability,and difficulty in uniform dispersion in the aluminum matrix,the preparation of Gr/Al powder has become a difficult problem in the application of SLM forming of additive manufacturing.

    As far as we konw,there is no report on the synthesis of Al/graphene composites by the electroless plating method.The purpose of this study is to prepare the graphene/aluminum composite powder by uniformlyplatingmetalaluminum atomson the surface of graphene by the electroless plating method.Then,it can be used to prepare Gr/Al with metal aluminum or aluminum alloy,which is expected to solve the problem of easy agglomeration of graphene in the aluminum matrix,improve the interface between graphene and aluminum matrix,and meet the requirements of SLM for materials.

    1 Experimental

    1.1 Materials and reagents

    The graphene/aluminum composite powder was prepared with aluminum powder(AR,purity 99.0%,purchased from Beijing Chemical Reagent Factory)and graphene (average layer 6 layers,Tangshan Jianhua Technology Development Co.,Ltd.).Anhydrous aluminum chloride (purchased from Tianjin Chemical Reagent Factory)and iodine(purchased from Zhengzhou Chemical Reagent Factory)were sealed and stored in a brown bottle as an initiator.Furthermore,commercial NaH(purity 60%,purchased from Aladdin)was stored under a N2atmosphere to prevent oxygen/moisture exposure.Ethyl bromide(EtBr)(AR,purchased from Damao Chemical Reagent Factory)was distilled over anhydrous calcium chloride under N2atmosphere to remove water.Toluene and tetrahydrofuran(THF)(AR,purchased from Damao ChemicalReagent Factory)were distilled on sodium metal under N2atmosphere to remove water.H2(purity 99.99%,purchased from Taiyuan Industrial Gas Factory)as shielding gas was dried using a drying device.

    1.2 Activation of aluminum powder

    All reactions were carried out in an anhydrous and anaerobic environment (hydrogen atmosphere).After repeated replacement with H2,3 g of aluminum powder,traces of anhydrous aluminum chloride and iodine (about 0.015 g),and 20 mL of freshly sealed ethidium bromide (EtBr)were added to a 250 mL three-necked flask.The mixture was heated to 39℃and refluxed under a stream of hydrogen with stirring.After about 30 min,the reaction started,and the white smoke appeared,and then the mixture turned slightly black.As a result,the aluminum powder began to be activated and gradually generated an alkyl aluminum sesquihalide and activated aluminum.After 90 min,15 mL of THF (as a complexing agent)was added to the reaction system,and the reaction was continued for 10 min.The mixture was quickly centrifuged,and the resulting supernatant (i.e.,alkylaluminum sesquihalide)was sealed and stored.

    1.3 Plating

    All reactions were carried out in an anhydrous and anaerobic environment(hydrogen atmosphere).0.2 g of graphene was weighed and added into 30 mL of toluene and the alkyl aluminum sesquihalide solution prepared in 1.2.The mixture was dispered uniformity by ultrasonic for 30 min,and 5.0 g of NaH was subsequently added,and the mixture was stirred and refluxed at 110℃for 90 min.After the reaction was completed,the mixture was filtered,washed with absolute ethanol and distilled water successively,and then the filter residue was freeze-dried.Finally,the graphene/aluminum composite powder was obtained.

    1.4 Characterization

    Fourier transform infrared (FTIR)spectra of the samples (4 000~500 cm-1) were measured on an FTIR-8400S infrared spectrometer using the KBr compression method.The microstructure and elemental composition of the samples were analyzed by the field emission scanning electron microscopy (SEM)(INSPECTF-50)(the acceleration voltage was 20 kV),energy dispersive spectroscopy (EDS)and selected area electron diffraction(SAED).The structures of the graphene and Al/graphene composite powder were examined using a Rigaku Ultima TypeⅣ X-ray diffractometer equipped with a Cu Kα radiation (λ=0.154 056 nm)with 40 kV of the working voltage,30 mA of the working current,5°~80°of the scanning range and 0.01°of the step size.The Raman spectra of the samples were determined using an inVia Reflex-type microscopic confocal laser Raman spectrometer with incident laser light at a wavelength of 532 nm.The porous structure of the sample was characterized by an ASAP2020 automatic specific surface area and porosity analyzer,and the specific surface area of the sample was determined.

    2 Results and discussion

    2.1 Surface analysis

    The graphene used in the experiment was a commercially available graphene,which was prepared by the redox method.Therefore,the oxygen-containing groups such as hydroxyl group,carbonyl group,and epoxy group were presented on the surface of the graphene.

    Fig.1 presentsthecomparison ofthe FTIR spectra of graphene and Al/graphene composite powder.Characteristic peaks of graphene in the infrared spectrum were observed forthe -OH stretching vibration absorption peak at 3 452 cm-1,and the C-O stretching vibration absorption peak at 1 125 cm-1.In addition,the absorption peaks at 1 648,1 639 and 1 546 cm-1were produced from the C=C stretching vibration of the sp2structure in graphene[20].No absorption peak corresponding to C=O was observed in Fig.1,indicating that the graphene that had been used was not graphene oxide.For the Al/graphene composite powder,all the characteristic peaks of the graphenewere weakened,especially the oxygencontaining groups because that the graphene was reduced by the reduction system and the surface and interlayersofthe graphenewere deposited with aluminum during electroless plating[21].Therefore,FTIR spectroscopy provided convincing evidence that graphene was indeed reduced by the system to facilitate electroless plating.

    Fig.2(a,b)show the SEM images of Al/graphene composite powder.It can be seen that the graphene was spatially curved after electroless aluminum plating to form pores of different sizes and irregularities.The formation of these pores could be attributed to the action of aluminum.Because the graphene is multilayered,the interlayer spacing was increased by ultrasound during the experiment.After the aluminum alkyl sesquihalide was reduced by NaH,the metal aluminum atomsweremorelikelytoenterthe interlayer voids,grow and extend,and interact with the defect regions in the graphene to generate a tensile force,which caused the graphene to bend and form ink-bottle-type pores.Fig.2(c,d)show the EDS spectra of spot 1 and spot 2 in Fig.2(a,b),respectively.The spot 1 was a point on the agglomerate of aluminum,which was very bright under electron microscopy.It can be seen from Fig.2(c)that the aluminum content was low,substantially existed in the form of alumina and contained a small amount of aluminum chloride,which indicated that the aluminum atom was staked and then oxidized.The spot 2 in Fig.2(b)was bright and the overall distribution was uniform.Fig.2(d)shows that the aluminum content was high and only a very small amount of aluminum was oxidized;furthermore,most of them still existed in an elemental form,indicating that the coating of graphene could protect the aluminum elementin the hole from being oxidized.There were a lot of spots the same as spot 2 after electroless plating.When Gr/Al is made of Al/graphene composite powder with aluminum or aluminum alloy,it can greatly improve the compatibility of graphene with metal and meet the requirements of the SLM for material.

    Fig.2 (a,b)SEM images of Al/graphene composite powder;(c)Composition analysis at spot 1;(d)Composition analysis at spot 2

    2.2 Structural analysis

    As shown in Fig.3(a),according to the classification method proposed by the International Union of Pure and Applied Chemistry,the adsorption isotherm curve of the Al/graphene composite powder presented typical typeⅣadsorption behaviors at-196℃and the H3-type hysteresis loop.The adsorption of N2molecules was single-layer and multi-layer adsorption in the micropores and mesopores,respectively,and the adsorption curve grew with a high slope in the relative pressure range of0 <P/P0<0.45,which indicated the large number of micropores and mesopores.In addition,these pores provided enough space to adsorb N2molecules.At the relative pressure range of 0.45<P/P0<1,the adsorption curve rised sharply,and unsaturation occured at the end of the curve.This situation indicated that a certain number of macropores were present in the sample,and the N2molecules caused capillary condensation in these pores,resulting in a significant increase in the amount of adsorption.Furthermore,as seen in Fig.3,there was a clear hysteresis loop,which proved the presence of open (parallel plate holes with four open sides)and the ink-bottle micro-and mesopores in the sample.The swelling of micropores and mesopores resulted in irreversible absorption of N2molecules in these pores.Besides, the irreversible chemical interactions between N2and the surface of the sample may also cause a hysteresis loop in the lower relative pressure range.Because of the presence of open(parallel plate holes with four open sides)and ink-bottle macro-pores and mesopores in the sample,the N2molecules showed capillary condensation, resulting in a significanthysteresisloop in thehigherrelative pressure range.

    As shown in Fig.3(b),the pore size distribution curveshowsthatthemesoporesand micropores accounted for the majority,and the maximum pore diameter was 1.6~3.7 nm.However,the curve was wide,and the pore diameter was not uniform.The Brunauer-Emmett-Teller specific surface area of the Al/graphene composite powder was 91 m2·g-1,which was much lower than the theoretical specific surface area of single-layer graphene.On the one hand,the graphene that has been used was multi-layered.On the other hand,graphene underwent spatial bending deformation to form a cladding structure after aluminum plating,so a large amount of surface area was not available for nitrogen adsorption.And this part of the surface area that could not be used for N2adsorption was combined with aluminum.So when Al/graphene composite powder is finally used for the preparation of Gr/Al,it can greatly improve the compatibility of graphene with the metal matrix.

    Fig.3 (a)N2adsorption-disorption isotherms of the Al/graphene composite powder;(b)Pore size distribution curve from the desorption branch

    Fig.4 Raman spectra of graphene and Al/graphene composite powder

    Fig.4 presents the Raman spectra of graphene and Al/graphene composite powder.The raw graphene exhibited a D band and G band at 1 332 and 1 566 cm-1in Fig.4(a),respectively,and the appearance of the D band indicated that the graphene was defective.The form of defects can be expressed as oxygencontaining groups, carbon-carbon double bonds,carbon five-membered rings,and carbon sevenmembered rings,which indirectly verify the correctness of the infrared spectra of Fig.1.The position of the G band appeared at 1 566 cm-1,which is lower than the literature[22](1 580 cm-1).The shape of the 2D band appearing at 2 677 cm-1was asymmetrical,indicating that the graphene used was a multilayered structure because the G band had red-shift with the increase of the number of graphene layers.Fig.4(b)shows that the peaks at 1 353 and 1 583 cm-1belong to D band and G band of the Al/graphene composite powder,respectively.Obviously,the Al/graphene composite powder had a blue-shift relative to the raw material graphene,and the D band and G band positions were almost identical to the single-layer graphene.The reason is that it could cause the pitch of the graphene layer to increase when the aluminum atoms entered into the interlayer of the graphene,exhibiting some of the properties of the single-layer graphene.

    It can be found that ID/IG(the intensity ratio of the D peak to the G peak)changed from 0.704 to 1.013,indicating that the degree and disorder of graphene defectswereincreased afterelectroless plating.

    Fig.5 presents the XRD patterns of the graphene and Al/graphene composite powder.The very weak diffraction peak at 2θ=10.9°corresponded to the(002)plane of graphene oxide,and the weak diffraction peak of the graphite(100)plane was located at 2θ=42.9°.Moreover,there was a broad but insufficiently strong diffraction peak at 2θ=24.0°,corresponding to the(002)plane of the expanded graphite;however,the 2θ angle of this diffraction peak was smaller than the theoretical value,and the interplanar spacing d=0.368 4 nm was calculated from the Bragg′s law.In summary,the graphene with low crystallinity was obtained by a redox method for graphite,and the oxygen-containing groups existed on the surface.

    Fig.5 XRD patterns of graphene and Al/graphene composite powder

    The characteristic peaks of Al were clearly discernible (PDF No.04-0787)in the XRD pattern of the Al/graphene composite powder.It can be seen from Fig.5 that there were four strong diffraction peaks for 2θ at 38.5°,44.7°,65.1°and 78.2°,corresponding to(111),(200),(220)and(311)plane,respectively.In addition,the diffraction peak of the(002)plane of the expanded graphite was located at 2θ=24.0°and the weak diffraction peak of the graphite(100)plane was located at 2θ=42.3°.However,the diffraction peaks corresponding to Al4C3were not detected.Briefly,the bonding between the graphene after aluminum plating and the aluminum is not based on chemical bonds but physical interactions.

    2.3 Microscopic surface analysis

    To analyze the adsorption of aluminum on the surface and layers of graphene,the following model assumptions were made:

    (1)The system is a constant temperature and pressure system that is not influenced by external factors;

    (2)There are α-phase (graphene phase)and βphase(metal aluminum phase),and the phase interface is SS,as shown in Fig.6;

    Fig.6 Schematic diagram of the surface phase

    (3)The phase between the AA surface and the BB surface in Fig.6 is the surface phase(including by-products such as sodium bromide and alkane of the reactions in the solution).The properties at AA surface are the same asthe α-phase and the properties at BB surface are identical with the βphase.Thus,all changes that occur at the interface are included in the surface phase.

    The volumes of the two phases from the bulk phases α and β to the SS face are represented by Vαand Vβ,respectively.Assuming that the concentrations are uniform in Vαand Vβ,the total amount of substance of component i in the whole system is ci,αVα+ci,βVβ,ci,αand ci,βare the concentrations of component i in the α-phase and β-phase,respectively.However,because the concentrations in the surface phase is not uniform,the value is different from the actual amount of substance(ni),and the difference is represented by ni,σ,then:

    This difference is the surface excess.The surface excessperunitarea,orthesurface excessof component i is:

    where A is the area of SS.

    The two-component systems have the following formula:

    where G is the free energy;μ is a chemical potential.

    For the surface phase,the surface energy σA also contributes to Gσ,so

    where Gσis the free energy of the surface phase,σ is the surface tension, μ1,σ, μ2,σare the chemical potential of component 1 and 2 in the surface phase,respectively.Because the system is equilibrated at a certain temperature and pressure,the chemical potentials μ1and μ2of the respective components are constant in each phase and interface.Under constant temperature and pressure conditions,if an infinitesimal change occurs in the system,according to formula(4),then:

    If there is only a slight change in the interface area in the system under constant temperature and pressure,the amount of substance of component 1 and 2 on the interface changes,so that the surface excesses n1,σand n2,σalso change accordingly.Minor changes in surface free energy should be:

    It can be derived from equations(5)and(6):

    Divide both ends by A and contact equation(2):

    Assuming that the position of the surface is selected as being where the surface excess of the solvent(component 1)is zero,which means Γ1=0,then equation(8)can be re-written as follow:

    At equilibrium,aluminum(component 2)has the same chemical potential in the surface phase and the bulk phase,ie., μ2,σ=μ2(in the bulk phase).In the bulk phase,-dμ=RTlnα2,brought into equation(9),

    where Γ2is the surface excess of aluminum, α2is the activity of aluminum in solution,σ is the surface tension of the solution,R is gas constant;T is thermodynamic temperature.The surface excess is much greater than the concentration of aluminum in the surface phase,at which point the surface excess can be approximated as the surface concentration.The concentration of aluminum(c)can be used instead of the activity α2,so the subscript is omitted under constant temperature conditions,and the formula(10)can be written as:

    where Γ is the adsorbing capacity,c is the concentration of solution.Because the aluminum obtained by the reduction is a solid and the concentration is constant (assuming 1),the formula (11)can be simplified as:

    where K is a positive constant.That is,the surface excess of aluminum in the graphene surface and interlayer is related to the rate of change of solvent surface tension.If the surface tension becomes smaller(dσ<0),the Γ is positive,which means that the concentration of aluminum in the surface layer is greaterthan in the solution,which ispositive adsorption;if the surface tension becomes larger,the Γ is negative,which means the concentration of aluminum in the surface layer is less than in the solution,which is negative adsorption.

    Fig.7 SEM images of the Al/graphene composite powder corresponding to the added amount of NaH

    For the experimental system,the addition or not of NaH and the amount of addition have a great influence on the change of the surface tension of the solution.When NaH was absent from the system,the active alkyl aluminum sesquihalide decomposed at high temperature,and molecular bromine was formed.Then,the molecular bromine reacted with a trace amount of water in the system to form a mineral acid.The presence of this acid increased the surface tension of the solution.As shown in Fig.7(a),graphene exhibited negative adsorption on aluminum,that is,it did notadsorb aluminum,so aluminum itself agglomerated.With the addition of NaH,the alkyl aluminum sesquihalide was reduced and decomposed,and some by-products were changed from molecular bromine to inorganic salt sodium bromide,so that the amount of inorganic acid formed was reduced,and the change of surface tension of the solution was smaller than before.The degree of agglomeration of aluminum wasweakened,and graphene begins to adsorb aluminum,as shown in Fig.7(b,c).When the added amount of NaH is slightly larger than the theoretical value,the reductive decomposition ofthe alkyl aluminum sesquihalide did notproducethe byproduct molecular bromine,which means the system did not contain a mineral acid.However,the presence of another by-product alkane reduced the surface tension ofthe solution,so thataluminum was adsorbed substantially on the surface and interlayers of the graphene without self-agglomeration,as shown in Fig.7(d).This situation is consistent with the ideal system assumption.As shown in Fig.7(e,f), with continuing to increase the amount of NaH,the extra NaH reduced the oxygen-containing groups of the graphene,so that the interlayer spacing becomes smaller,the force become larger,and the formed graphene/Al new phase was agglomerated.

    3 Conclusions

    Novel Al/graphene composite powder was prepared by a new organic phase electroless aluminum plating method in the current study.It is not necessary to perform any pretreatment(sensitization or activation)on graphene.At high temperature,the alkyl aluminum sesquihalide was decomposed and reduced to aluminum atoms by NaH,and the aluminum atoms adsorbed and deposited on the defects of the graphene.Ultrasound increased the spacing of the graphene layer,and the interaction of the aluminum atoms with the defect region caused the graphene sheet to be bent and formed a cladding structure.Microscopic surface analysis shows that the adsorption of aluminum by graphene is related to the rate of change of the surface tension of the solution.The situation that the surface tension of the solution become smaller that could facilitate the adsorption.Theaddition ofNaH can notonlyreducethe activation energy ofaluminum produced by the decomposition of the alkyl aluminum sesquihalide,but also indirectly reduce the surface tension of the solution.When the added amount of NaH was slightly larger than the theoretical value,the aluminum plating effect was the best,and no agglomeration occured.Consequently,the advantages of a relatively uniform distribution of Al on the surface and interlayers of graphene as well as special porous structure and high specific surface area may provide some information for solving the problems of the further preparation of Gr/Al,such as easy agglomeration of graphene in the aluminum matrix,and not being firmly bonded on the interface between the graphene and the matrix.

    猜你喜歡
    鍍鋁中北大學理學院
    《中北大學學報(社會科學版)》征稿啟事
    昆明理工大學理學院學科簡介
    昆明理工大學理學院簡介
    檸檬酸輔助可控制備花狀銀粒子及其表面增強拉曼散射性能
    車燈塑料件真空鍍鋁缺陷分析與對策
    電鍍與涂飾(2021年2期)2021-03-08 14:35:18
    中北大學信創(chuàng)產(chǎn)業(yè)學院入選首批現(xiàn)代產(chǎn)業(yè)學院
    科學導報(2021年91期)2021-01-11 07:02:14
    河鋼集團國內(nèi)首發(fā)300 g/m2超厚鍍層鍍鋁板
    鋁加工(2020年6期)2020-12-20 14:08:41
    《中北大學學報(自然科學版)》征稿簡則
    西安航空學院專業(yè)介紹
    ———理學院
    三層結(jié)構(gòu)鍍鋁復合膜中鍍鋁面與PE膜復合的技術(shù)風險
    av超薄肉色丝袜交足视频| 十八禁网站免费在线| 国产真人三级小视频在线观看| 国产高清视频在线播放一区| 超碰97精品在线观看| 国产真人三级小视频在线观看| 天天添夜夜摸| 国产精品秋霞免费鲁丝片| 国产日韩一区二区三区精品不卡| 欧美日韩精品网址| 美女大奶头视频| 国产亚洲欧美在线一区二区| 国产成人av教育| 丰满迷人的少妇在线观看| 亚洲国产精品合色在线| 国产一区在线观看成人免费| 丝袜美腿诱惑在线| 狠狠狠狠99中文字幕| 精品福利永久在线观看| 国产熟女xx| 满18在线观看网站| 成在线人永久免费视频| 91麻豆精品激情在线观看国产 | 亚洲午夜精品一区,二区,三区| 亚洲精华国产精华精| 90打野战视频偷拍视频| 91麻豆精品激情在线观看国产 | 久久99一区二区三区| 免费高清视频大片| 日韩欧美一区视频在线观看| 天天影视国产精品| 国产高清视频在线播放一区| 999久久久国产精品视频| 成人国产一区最新在线观看| 成人免费观看视频高清| 国产精品美女特级片免费视频播放器 | 99国产极品粉嫩在线观看| 男女做爰动态图高潮gif福利片 | 91成年电影在线观看| 亚洲aⅴ乱码一区二区在线播放 | 午夜日韩欧美国产| 日韩中文字幕欧美一区二区| 国产蜜桃级精品一区二区三区| av在线天堂中文字幕 | 高清在线国产一区| 一本综合久久免费| 日本五十路高清| 久热这里只有精品99| 亚洲精品中文字幕一二三四区| 国产精品美女特级片免费视频播放器 | 老汉色av国产亚洲站长工具| 日韩av在线大香蕉| 可以免费在线观看a视频的电影网站| 高清欧美精品videossex| 女人被躁到高潮嗷嗷叫费观| 国产精品二区激情视频| 国产精华一区二区三区| 美女福利国产在线| 欧美成人午夜精品| 精品一品国产午夜福利视频| 亚洲精华国产精华精| 国产成人欧美在线观看| 午夜福利影视在线免费观看| 亚洲精品成人av观看孕妇| 欧美黑人精品巨大| 亚洲五月天丁香| 在线av久久热| 午夜激情av网站| 国产亚洲精品第一综合不卡| 黄色视频,在线免费观看| 亚洲人成伊人成综合网2020| 久久精品国产综合久久久| 亚洲成人免费电影在线观看| 99久久人妻综合| 日日爽夜夜爽网站| 国产精品永久免费网站| 两人在一起打扑克的视频| 中文字幕色久视频| 一区二区三区精品91| 天堂中文最新版在线下载| 国产精品国产高清国产av| 搡老乐熟女国产| 无人区码免费观看不卡| 午夜精品在线福利| 久久天躁狠狠躁夜夜2o2o| 99riav亚洲国产免费| av网站免费在线观看视频| 国产精品 国内视频| 免费高清在线观看日韩| 亚洲五月天丁香| 日韩大码丰满熟妇| 老司机福利观看| 丰满的人妻完整版| 男女做爰动态图高潮gif福利片 | 十分钟在线观看高清视频www| 亚洲五月婷婷丁香| 欧美精品一区二区免费开放| 99国产精品一区二区蜜桃av| 日本免费a在线| 日本a在线网址| 亚洲av第一区精品v没综合| 久久人妻福利社区极品人妻图片| 国产免费现黄频在线看| 亚洲av熟女| 久久草成人影院| 亚洲专区字幕在线| 啦啦啦免费观看视频1| 精品国产乱码久久久久久男人| 免费在线观看黄色视频的| 精品国产国语对白av| 亚洲全国av大片| 日本黄色日本黄色录像| 女警被强在线播放| 99国产精品一区二区三区| 国产精品久久久av美女十八| 亚洲精华国产精华精| 国产在线精品亚洲第一网站| 色哟哟哟哟哟哟| 亚洲av成人av| 国产亚洲欧美98| 精品卡一卡二卡四卡免费| 成人三级黄色视频| 欧美在线一区亚洲| 国产精品久久电影中文字幕| 久久香蕉精品热| 国产免费av片在线观看野外av| 大型av网站在线播放| www.熟女人妻精品国产| 不卡一级毛片| 琪琪午夜伦伦电影理论片6080| 免费在线观看亚洲国产| 免费在线观看视频国产中文字幕亚洲| 另类亚洲欧美激情| 久久久久国内视频| 人人妻人人添人人爽欧美一区卜| 人人妻,人人澡人人爽秒播| 免费高清在线观看日韩| 成人影院久久| 国产99白浆流出| 美女高潮喷水抽搐中文字幕| 欧美日韩一级在线毛片| 9热在线视频观看99| 午夜福利欧美成人| 成人手机av| 久久热在线av| 午夜精品国产一区二区电影| 国产精品爽爽va在线观看网站 | 在线永久观看黄色视频| 高清毛片免费观看视频网站 | 美女午夜性视频免费| 久久精品国产亚洲av高清一级| www.熟女人妻精品国产| 少妇粗大呻吟视频| 亚洲性夜色夜夜综合| 成人亚洲精品av一区二区 | 视频在线观看一区二区三区| 成人18禁高潮啪啪吃奶动态图| 纯流量卡能插随身wifi吗| 啦啦啦 在线观看视频| 女警被强在线播放| 亚洲国产欧美网| 日韩成人在线观看一区二区三区| 电影成人av| 精品国内亚洲2022精品成人| 婷婷精品国产亚洲av在线| 国产av精品麻豆| 亚洲第一欧美日韩一区二区三区| 亚洲五月色婷婷综合| 国产一区二区在线av高清观看| 国产成人av教育| 久久精品国产综合久久久| 日韩 欧美 亚洲 中文字幕| 男女下面插进去视频免费观看| 亚洲精品国产一区二区精华液| 精品一区二区三区视频在线观看免费 | 国产黄a三级三级三级人| 久久久国产成人免费| 中文字幕精品免费在线观看视频| 婷婷六月久久综合丁香| 久9热在线精品视频| 一本综合久久免费| 1024香蕉在线观看| 一进一出抽搐动态| 9热在线视频观看99| 一a级毛片在线观看| 欧美精品一区二区免费开放| 99久久99久久久精品蜜桃| 久久精品国产亚洲av香蕉五月| 日韩人妻精品一区2区三区| 久久国产精品人妻蜜桃| 国产精品影院久久| 又大又爽又粗| 日韩国内少妇激情av| 国产不卡一卡二| 这个男人来自地球电影免费观看| 一本综合久久免费| 欧美激情 高清一区二区三区| 99久久国产精品久久久| 美女国产高潮福利片在线看| videosex国产| 黑人猛操日本美女一级片| 欧美+亚洲+日韩+国产| 久久久精品欧美日韩精品| 69精品国产乱码久久久| 成人手机av| 搡老岳熟女国产| 美女国产高潮福利片在线看| 亚洲欧美激情在线| 亚洲成人精品中文字幕电影 | 美女国产高潮福利片在线看| 9色porny在线观看| 日日夜夜操网爽| 午夜激情av网站| 黄色视频不卡| 久久 成人 亚洲| 欧美+亚洲+日韩+国产| 成在线人永久免费视频| 亚洲精品久久午夜乱码| 精品久久久久久,| a在线观看视频网站| 亚洲精品久久午夜乱码| 婷婷六月久久综合丁香| 日本撒尿小便嘘嘘汇集6| 岛国在线观看网站| 亚洲成av片中文字幕在线观看| 国产精品美女特级片免费视频播放器 | 国产伦人伦偷精品视频| 成人国语在线视频| 看黄色毛片网站| 亚洲国产看品久久| 中文欧美无线码| 热99国产精品久久久久久7| 日韩欧美三级三区| 国产精品亚洲av一区麻豆| 国产精品亚洲一级av第二区| 成年人免费黄色播放视频| 亚洲精品国产一区二区精华液| 国产视频一区二区在线看| 在线天堂中文资源库| 亚洲国产中文字幕在线视频| 欧美+亚洲+日韩+国产| 久久久久国内视频| 日日摸夜夜添夜夜添小说| 国产精品久久久av美女十八| 日韩有码中文字幕| 成年版毛片免费区| 91成年电影在线观看| √禁漫天堂资源中文www| 天堂俺去俺来也www色官网| 精品国产乱码久久久久久男人| 欧美日韩亚洲国产一区二区在线观看| 好男人电影高清在线观看| 18禁美女被吸乳视频| 国产人伦9x9x在线观看| 午夜影院日韩av| 麻豆国产av国片精品| 亚洲自偷自拍图片 自拍| 成年人免费黄色播放视频| av片东京热男人的天堂| 国产欧美日韩一区二区三区在线| 99国产精品一区二区蜜桃av| 婷婷丁香在线五月| 欧美日本亚洲视频在线播放| 久9热在线精品视频| 亚洲精品一卡2卡三卡4卡5卡| 老汉色av国产亚洲站长工具| 男女高潮啪啪啪动态图| 国产三级在线视频| 国产成人精品无人区| 亚洲精品久久午夜乱码| 国产成人系列免费观看| www.www免费av| 91精品国产国语对白视频| 亚洲成人国产一区在线观看| 亚洲第一欧美日韩一区二区三区| 村上凉子中文字幕在线| 两性夫妻黄色片| 精品福利观看| 免费高清在线观看日韩| 精品高清国产在线一区| 久久中文看片网| 日韩有码中文字幕| 99久久久亚洲精品蜜臀av| 久久精品人人爽人人爽视色| 啦啦啦在线免费观看视频4| 午夜影院日韩av| 操出白浆在线播放| 午夜两性在线视频| 色精品久久人妻99蜜桃| 无限看片的www在线观看| 亚洲激情在线av| 成人亚洲精品av一区二区 | 国产精品美女特级片免费视频播放器 | 黄色丝袜av网址大全| 老熟妇仑乱视频hdxx| 天天添夜夜摸| 人人妻人人添人人爽欧美一区卜| 国产主播在线观看一区二区| 国产精品亚洲av一区麻豆| 妹子高潮喷水视频| 亚洲一码二码三码区别大吗| 色婷婷久久久亚洲欧美| 免费高清在线观看日韩| 色播在线永久视频| 黄片小视频在线播放| 成人三级做爰电影| 丝袜在线中文字幕| 中亚洲国语对白在线视频| 香蕉久久夜色| 日本黄色日本黄色录像| 看免费av毛片| 1024香蕉在线观看| 高清在线国产一区| 国产一区在线观看成人免费| 亚洲欧美激情综合另类| 亚洲国产欧美日韩在线播放| 男女之事视频高清在线观看| 看黄色毛片网站| 久久中文看片网| 久久伊人香网站| 国产深夜福利视频在线观看| 真人一进一出gif抽搐免费| 一边摸一边抽搐一进一出视频| 国产精品九九99| 丰满人妻熟妇乱又伦精品不卡| 午夜福利欧美成人| 欧美丝袜亚洲另类 | 欧美人与性动交α欧美软件| 在线天堂中文资源库| 色综合欧美亚洲国产小说| 无遮挡黄片免费观看| 午夜精品在线福利| 日本黄色视频三级网站网址| 精品福利永久在线观看| 97人妻天天添夜夜摸| 久久中文字幕一级| 在线国产一区二区在线| 亚洲熟妇中文字幕五十中出 | 婷婷精品国产亚洲av在线| 色精品久久人妻99蜜桃| 欧美不卡视频在线免费观看 | 亚洲精品av麻豆狂野| 午夜福利欧美成人| 老司机午夜福利在线观看视频| 丝袜在线中文字幕| 亚洲一卡2卡3卡4卡5卡精品中文| 欧美日韩黄片免| 十八禁人妻一区二区| 超碰成人久久| 亚洲第一青青草原| 国产精品永久免费网站| 97碰自拍视频| 中文字幕人妻熟女乱码| 黑人巨大精品欧美一区二区蜜桃| 69精品国产乱码久久久| 日本黄色视频三级网站网址| 国产亚洲欧美在线一区二区| 老司机午夜福利在线观看视频| netflix在线观看网站| 亚洲伊人色综图| 天堂√8在线中文| 精品电影一区二区在线| 精品乱码久久久久久99久播| 69精品国产乱码久久久| av电影中文网址| 亚洲精品一区av在线观看| 一区二区日韩欧美中文字幕| 亚洲精品粉嫩美女一区| 国产成人av教育| 国产伦一二天堂av在线观看| av中文乱码字幕在线| 日韩欧美免费精品| 精品久久蜜臀av无| 午夜激情av网站| 精品国产一区二区三区四区第35| 亚洲一码二码三码区别大吗| 午夜久久久在线观看| 看黄色毛片网站| 日韩欧美国产一区二区入口| 美女高潮到喷水免费观看| 成年女人毛片免费观看观看9| 咕卡用的链子| 国产一区在线观看成人免费| 日本vs欧美在线观看视频| 人人妻,人人澡人人爽秒播| av福利片在线| 国产精品99久久99久久久不卡| 最近最新中文字幕大全免费视频| 好看av亚洲va欧美ⅴa在| 精品国产乱码久久久久久男人| 麻豆一二三区av精品| 国产一区二区激情短视频| 亚洲欧美日韩高清在线视频| 国产精品九九99| 人人妻人人添人人爽欧美一区卜| 国产主播在线观看一区二区| 日本三级黄在线观看| 久久国产乱子伦精品免费另类| 最新在线观看一区二区三区| 欧美+亚洲+日韩+国产| 极品人妻少妇av视频| 女人被躁到高潮嗷嗷叫费观| 无人区码免费观看不卡| 好男人电影高清在线观看| 老司机午夜十八禁免费视频| 久久久久亚洲av毛片大全| 久久久精品国产亚洲av高清涩受| 亚洲 国产 在线| 99riav亚洲国产免费| 一区二区三区激情视频| 久久精品成人免费网站| 久久久久久免费高清国产稀缺| 日韩大码丰满熟妇| 成人av一区二区三区在线看| 欧美成狂野欧美在线观看| 黄色 视频免费看| 中文欧美无线码| 国产高清视频在线播放一区| av福利片在线| ponron亚洲| 久久久国产成人免费| 激情在线观看视频在线高清| 久久久久久久精品吃奶| 国产成人精品久久二区二区免费| 成人亚洲精品一区在线观看| 久久久久精品国产欧美久久久| 美女高潮喷水抽搐中文字幕| 啦啦啦在线免费观看视频4| 亚洲熟妇中文字幕五十中出 | 男女下面进入的视频免费午夜 | 天堂√8在线中文| 可以在线观看毛片的网站| 十八禁网站免费在线| 啦啦啦在线免费观看视频4| 99国产精品免费福利视频| 亚洲avbb在线观看| 国产欧美日韩一区二区三| 久久国产精品人妻蜜桃| 长腿黑丝高跟| 制服人妻中文乱码| 欧美日本中文国产一区发布| 久久国产精品人妻蜜桃| 欧美激情 高清一区二区三区| 97超级碰碰碰精品色视频在线观看| 色综合站精品国产| 我的亚洲天堂| 国产成人精品在线电影| 国产熟女xx| 欧美在线一区亚洲| 午夜激情av网站| 久久九九热精品免费| 精品一区二区三区视频在线观看免费 | 97超级碰碰碰精品色视频在线观看| 99久久久亚洲精品蜜臀av| 国产精品秋霞免费鲁丝片| 午夜影院日韩av| 国产精品久久电影中文字幕| 国产精品久久久人人做人人爽| 50天的宝宝边吃奶边哭怎么回事| 国产精品香港三级国产av潘金莲| 女人精品久久久久毛片| 国产亚洲欧美98| 亚洲中文日韩欧美视频| 天天影视国产精品| 国产欧美日韩一区二区精品| 夜夜躁狠狠躁天天躁| 80岁老熟妇乱子伦牲交| 在线观看日韩欧美| 老司机在亚洲福利影院| 少妇裸体淫交视频免费看高清 | 国产精品国产高清国产av| 一区二区日韩欧美中文字幕| 狂野欧美激情性xxxx| 亚洲精品在线美女| 18禁美女被吸乳视频| 男男h啪啪无遮挡| 欧美激情高清一区二区三区| 女人爽到高潮嗷嗷叫在线视频| 日韩av在线大香蕉| 欧美成人午夜精品| 亚洲人成伊人成综合网2020| 色在线成人网| 最新美女视频免费是黄的| 日本精品一区二区三区蜜桃| 在线国产一区二区在线| 90打野战视频偷拍视频| 中文字幕精品免费在线观看视频| 亚洲七黄色美女视频| 女人爽到高潮嗷嗷叫在线视频| 亚洲欧美一区二区三区黑人| 一级毛片高清免费大全| 国产精品久久久久久人妻精品电影| 久久国产精品影院| 久久久精品国产亚洲av高清涩受| 嫩草影视91久久| 精品欧美一区二区三区在线| 精品国产一区二区三区四区第35| 亚洲欧美日韩高清在线视频| 91成年电影在线观看| 国产精品久久久久成人av| 天天添夜夜摸| 真人做人爱边吃奶动态| 男女之事视频高清在线观看| 黄网站色视频无遮挡免费观看| 真人一进一出gif抽搐免费| 亚洲成人免费av在线播放| 国产97色在线日韩免费| 亚洲国产看品久久| xxx96com| 嫩草影院精品99| 超碰成人久久| 嫁个100分男人电影在线观看| 12—13女人毛片做爰片一| 两人在一起打扑克的视频| 男人舔女人下体高潮全视频| 成人18禁在线播放| www.999成人在线观看| 黄色怎么调成土黄色| 成年人免费黄色播放视频| 免费观看精品视频网站| 亚洲国产精品一区二区三区在线| 亚洲五月色婷婷综合| 美女 人体艺术 gogo| 久久国产乱子伦精品免费另类| 91大片在线观看| 国产精品二区激情视频| 欧美乱色亚洲激情| 高清毛片免费观看视频网站 | av免费在线观看网站| 午夜福利,免费看| 欧美大码av| 日韩精品免费视频一区二区三区| 精品久久久久久成人av| 婷婷精品国产亚洲av在线| 99热国产这里只有精品6| 亚洲国产欧美日韩在线播放| 久久久国产精品麻豆| 日韩欧美在线二视频| 午夜福利欧美成人| e午夜精品久久久久久久| 好男人电影高清在线观看| 18禁黄网站禁片午夜丰满| 成人特级黄色片久久久久久久| 一边摸一边抽搐一进一小说| 精品福利观看| 午夜亚洲福利在线播放| 成人永久免费在线观看视频| 一个人免费在线观看的高清视频| 国产成人免费无遮挡视频| 亚洲中文av在线| 淫妇啪啪啪对白视频| 久久精品国产亚洲av香蕉五月| 丰满人妻熟妇乱又伦精品不卡| av欧美777| 亚洲精品国产色婷婷电影| 国产xxxxx性猛交| 多毛熟女@视频| av有码第一页| 不卡av一区二区三区| 免费看十八禁软件| 黑人巨大精品欧美一区二区mp4| 精品一区二区三区四区五区乱码| 久久国产精品男人的天堂亚洲| 亚洲情色 制服丝袜| 午夜亚洲福利在线播放| 亚洲欧美激情在线| 成年女人毛片免费观看观看9| 一进一出好大好爽视频| 一本综合久久免费| 又大又爽又粗| 天天躁狠狠躁夜夜躁狠狠躁| 久久久久国产一级毛片高清牌| 国产不卡一卡二| 看免费av毛片| 亚洲七黄色美女视频| 天堂俺去俺来也www色官网| 99久久精品国产亚洲精品| 搡老岳熟女国产| 精品一区二区三区av网在线观看| 高清黄色对白视频在线免费看| 亚洲中文字幕日韩| 欧美中文日本在线观看视频| 午夜福利欧美成人| 国产1区2区3区精品| 这个男人来自地球电影免费观看| 大型黄色视频在线免费观看| 国产精品一区二区在线不卡| 女生性感内裤真人,穿戴方法视频| 精品福利观看| 这个男人来自地球电影免费观看| 久久国产乱子伦精品免费另类| 午夜免费鲁丝| а√天堂www在线а√下载| 999久久久国产精品视频| 老司机福利观看| 91成年电影在线观看| 午夜激情av网站| 女人精品久久久久毛片| 亚洲精品久久成人aⅴ小说| 欧美乱码精品一区二区三区| 欧美在线一区亚洲| 神马国产精品三级电影在线观看 | 国产精品国产av在线观看| 亚洲av片天天在线观看| 亚洲精华国产精华精| 亚洲成人免费av在线播放| av天堂久久9| 久久久国产精品麻豆| 变态另类成人亚洲欧美熟女 | 色精品久久人妻99蜜桃| 激情视频va一区二区三区| 欧美日韩一级在线毛片| 久久精品国产清高在天天线| www日本在线高清视频| 91av网站免费观看|