碳纳米管表面改性工艺参数优化试验研究

利用超声分散法对团聚的原始碳纳米管分散处理后,通过酸化、敏化、活化等步骤对其进行表面改性处理,采用表面化学镀在其表面镀覆镍层,并进行热处理.研究了碳纳米管的分散、表面改性和镀镍工艺对镀层质量的影响.实验结果表明:在乙醇溶液中,利用分散剂进行超声分散可以明显改善碳纳米管之间的团聚状况;经过酸化、敏化、活化处理后其表面可形成密集的活化点;镀镍温度在20℃左右,pH值约8.2时,所得镀层较为均匀,经410℃保温2h的热处理后,镀层变得光滑、连续、致密,镀层的厚度为12～20nm.     

Simulation for Carbon Nanotube Dispersion and Microstructure Formation in CNTs/AZ91D Composite Fabricated by Ultrasonic Processing

The dispersion of carbon nanotubes (CNTs) in AZ91D melt by ultrasonic processing and microstructure formation of CNTs/AZ91D composite were studied using numerical and physical simulations. The sound field and acoustic streaming were predicted using finite element method. Meanwhile, optimal immersion depth of the ultrasonic probe and suitable ultrasonic power were obtained. Single-bubble model was used to predict ultrasonic cavitation in AZ91D melt. The relationship between sound pressure amplitude and ultrasonic cavitation was established. Physical simulations of acoustic streaming and ultrasonic cavitation agreed well with the numerical simulations. It was confirmed that the dispersion of carbon nanotubes was remarkably improved by ultrasonic processing. Microstructure formation of CNTs/AZ91D composite was numerically simulated using cellular automation method. In addition, grain refinement was achieved and the growth of dendrites was changed due to the uniform dispersion of CNTs.     

十二烷基硫酸钠对碳纳米管悬浮液分散性能的影响

以十二烷基硫酸钠(SDS)为分散剂,制备碳纳米管悬浮液。通过测定SDS在碳纳米管表面的等温吸附曲线和悬浮液的Zeta电位,研究SDS对碳纳米管表面性质的影响。结果表明:SDS的加入使Zeta电位由-28 mV变为-48 mV左右,SDS浓度c(SDS)为2.0×10-3 mol/L左右时达到最大电位值并最终趋于稳定;SDS在碳纳米管表面的等温吸附曲线为典型的双平台型(LS型)吸附曲线。SDS吸附量在低浓度下(0.7×10-3~1.2×10-3 mol/L范围内)处于第一平台吸附值;随后SDS浓度进一步增大,吸附量迅速上升,在2×10-3 mol/L处趋近饱和吸附,吸附量达到第2个平台。悬浮碳纳米管浓度测定结果表明SDS可作为水性体系碳纳米管的分散剂,SDS的最佳浓度范围为2.0×10-3~8.0×10-3 mol/L,通过静电排斥和位阻效应有效阻止碳纳米管的团聚。     

微波烧结温度对CNTs/Cu复合材料结构和性能的影响

结合液相混合方法、微波烧结技术和冷轧技术制备碳纳米管增强铜基（carbon nanotubes reinforced copper-matrix,CNTs/Cu）复合材料,研究不同烧结温度对于CNTs/Cu复合材料微观形貌、力学性能及物理性能的影响。结果表明,采用液相混合法制备出粒径为200~500 nm、碳纳米管质量分数为0.5%的CNTs/Cu复合粉体,碳纳米管均匀分散在铜颗粒中,并与之形成良好结合界面。CNTs/Cu复合材料的相对密度、硬度、电导率随着烧结温度的升高先增大后减小,在烧结温度为1000℃时达到最佳。制备的碳纳米管质量分数为0.5%的CNTs/Cu复合材料组织均匀、孔隙数量及尺寸较少,相对密度为95.79%,硬度为HV 80.9,电导率为81.8% IACS。经冷轧处理后,CNTs/Cu复合材料拉伸强度达到218 MPa,延伸率保持37.75%。由此可见,微波烧结技术是一种制备高性能CNTs/Cu复合材料的理想方法。     

Diameter-Controlled Growth of Carbon Nanotubes Through Pyrolysis of Acetylene Using Rare Earth Alloy as Catalyst in Hydrogen

Carbonnanotubes[1] (CNTs)havenovelquasione dimensionhollowstructurewithsmalldensity ,largeratioofsurfacetovolume ,highmechanicalstrength ,goodconductivityandchemicalstability .CNTshavepotentialapplicationsinmakingcatalystcarrier ,fabricatingnanoelectronics ,manufacturinghigh densityenergystoragematerial ,constructinghigh strengthcompositematerial ,andpreparingelec tromagneticwaveabsorptionmaterial[2～ 8] .InordertostudytheperformanceandapplicationofCNTs ,itisimportanttofindouthowtosynthesiz…     

碳纳米管表面辐照接枝改性及负载纳米铜的研究

采用硝酸(1∶1)对碳纳米管进行氧化纯化处理,然后采用~(60)Coγ射线辐照,引发丙烯酸单体在碳纳米管表面发生自由基加成、聚合反应,对碳纳米管表面进行表面改性,所得碳纳米管在水溶液中有良好的分散性。红外光谱证实C(=O)-H、C-OH等基团接枝到碳纳米管表面,表面改性前后的碳纳米管表面增强拉曼光谱(SERS)也存在显著差异。SEM研究结果表明,改性后的碳纳米管表面可以直接镀上连续、均匀的纳米铜颗粒,实现良好的异质连接。谢乐公式计算出铜晶粒平均大小为44.298nm。     

ACF/CNT复合材料的制备及其对Cr(Ⅵ)的吸附性能

以硝酸镍为催化剂前驱体,C2H2为碳源,H2为还原气,N2为载气,采用化学气相沉积法(CVD)在活性炭纤维(ACFs)毡体的纤维表面催化生长碳纳米管(CNTs),制备ACF/CNT复合材料。经测定,所制复合材料比表面积可达62.56 m2/g;扫描电镜分析表明,CNTs在ACFs表面分布均匀而致密,经过表面修饰可以作为1种良好的吸附材料。选择低浓度的六价铬(Cr(Ⅵ))溶液进行吸附研究,考察振荡时间、溶液pH值以及溶液的初始浓度等因素对吸附行为的影响。实验结果表明,初始Cr(Ⅵ)浓度为1 mg/L,在25℃时,随着振荡时间的增长溶液中Cr(Ⅵ)的脱除率逐渐增加,在150 min时达到最大值49.48%。溶液中Cr(Ⅵ)的脱除率随着pH的减小而增大,当pH值为2.0时脱除率达91.50%,对Cr(Ⅵ)的吸附量随着溶液初始浓度的增加而增大,但是当初始浓度到达5.0 mg/L时,脱除效率到达最大值后开始降低。并对ACF/CNT复合材料的吸附机制进行了探讨。     

不同纳米相增强铜基复合材料的性能

采用粉末冶金法,制备纳米SiO2颗粒(n-SiO2)、纳米SiC晶须(n-SiCw)和碳纳米管(CNTs)3种不同形态纳米相增强铜基复合材料,通过光学显微镜(OM)、扫描电镜(SEM)和球/盘式摩擦磨损试验机等测试手段研究纳米添加相对铜基复合材料显微组织、物理性能和摩擦学性能的影响。结果表明,纳米相可以显著提高铜基复合材料的硬度,其中n-SiCw的增强效果优于n-SiO2和CNTs;CNTs/Cu的减摩耐磨效果优于SiO2/Cu和SiCw/Cu;0.75%-CNTs/Cu(质量分数)复合材料具有高的硬度、优良的减摩耐磨性能,是综合性能最佳的复合材料。     

Preparation and CO conversion activity of ceria nanotubes by carbon nanotubes templating method

Ceria nanotubes with high CO conversion activity by means of carbon nanotubes as removable templates in the simple liquid phase process were fabricated under moderate conditions. The pristine CNTs were first pretreated by refluxing in a 30% nitric acid solution at 140 ℃ for 24 h, then dispersed in an ethanolic Ce（NO3）3.6H2O solution with ultrasonic radiation at room temperature for 1 h. Under vigorous stirring, NaOH solution was added drop by drop into the above ethanolic solution until the pH value was 10. The product was collected and repeatedly washed with ethanol and on drying at 60 ℃, the CeO2/CNT composites were obtained. Then, the as-prepared composites were heated at 450 ℃ in an air atmosphere for 30 min to remove CNTs. The ceria nanotubes were characterized by X-Ray Diffraction （XRD）, Transmission Electron Microscopy （TEM）, and X-Ray Photoelectron Spectrum （XPS）. The results showed that the ceria nanotubes were polycrystalline face-centered cubic phase and were composed of lots of dense cefia nanoparficles. The diameter of cefia nanotubes was about 40-50 nm. Catalytic activity of the product for CO oxidation was carded out at the region of 30-300 ℃ in a U-shaped quartz reactor with feeding about 0.15 g of the catalyst, which was loaded on Al2O3 carder. The inlet gas composition was 1.0% CO and 28% O2 with N2 as balance, and the rate of flow was kept at 40 ml/min. The catalytic products were analyzed by gas chromatography. The as-repared CeO2 nanotubes showed higher CO oxidation activity, which indicated that the morphology of ceria products affected the catalytic performance. The ceria nanotubes supported on Al2O3 demonstrated that conversion temperature for CO oxidation to CO2 was lower than that for bulk catalysts.     

轧制对纳米碳管弥散强化铜基复合材料微观组织的影响

利用粉末冶金工艺结合轧制退火工艺制备了纳米碳管弥散强化铜复合材料, 研究了轧制对纳米碳管在铜基体中分布的影响。材料冷轧轧下量60%时, 含纳米碳管0.3%的铜基复合材料致密度由轧制前的78.7%提高到98.9%, 同时显微硬度由HV49.2上升到96.4。扫描电镜照片表明, 随着纳米碳管分数增多、轧制量增大, 复合材料微观组织中出现的孪晶数目增多。孪晶引起的晶粒细化并通过纳米碳管弥散强化而保持, 可能是纳米碳管铜复合材料增强的机制。     

Generation of Temperature Dependent Transversely Isotropic Properties for Zigzag and Armchair Single-Walled Carbon Nanotubes

Finite element analysis has been carried out to obtain temperature dependent transversely isotropic properties of the single-walled carbon nanotubes (SWCNTs). Finite element models of SWCNTs are generated by specifying the C–C bond rigidities. The five independent transversely isotropic properties for different chiralities are evaluated using the stress fields of thick-walled cylinders and the elastic deformations of SWCNTs subjected to pure extension, internal pressure and pure torsion loads. Empirical relations are provided for the five independent elastic constants useful to armchair and zigzag SWCNTs.     

Effect of Multiwalled Carbon Nanotubes on the Thermal Conductivity and Porosity Characteristics of Blast Furnace Carbon Refractories

Different amounts of carbon nanotubes (CNTs) (0–5 mass pct) containing carbon refractory specimens for a blast furnace were prepared and coked for 3 hours at 1473 K (1200 °C) and 1673 K (1400 °C). The thermal conductivity and porosity characteristics of the coked specimens were evaluated using the flash diffusivity technique and mercury porosimetry, respectively. It was found that CNTs acted as carbon source, and most of them were consumed during coking. With the increase of CNT content, the aggregation of CNTs became more severe, the amount of SiC whiskers formed increased and their aspect ratio became larger, and the SiC whiskers tended to be distributed nonhomogeneously. The thermal conductivity of a 4 mass pct CNT containing a carbon specimen was highest because of the contributions of SiC and residual CNTs. The porosity characteristics of a 0.5 mass pct CNT containing a carbon specimen was best because of the uniform filling of SiC whiskers. The excessive addition of CNTs degraded the porosity characteristics because of the severe aggregation of CNTs.     

Hot Extrusion of A356 Aluminum Metal Matrix Composite with Carbon Nanotube/Al2O3 Hybrid Reinforcement

Over the years, the attention of material scientists and engineers has shifted from conventional composite materials to nanocomposite materials for the development of light weight and high-performance devices. Since the discovery of carbon nanotubes (CNTs), many researchers have tried to fabricate metal matrix composites (MMCs) with CNT reinforcements. However, CNTs exhibit low dispersibility in metal melts owing to their poor wettability and large surface-to-volume ratio. The use of an array of short fibers or hybrid reinforcements in a preform could overcome this problem and enhance the dispersion of CNTs in the matrix. In this study, multi-walled CNT/Al₂O₃ preform-based aluminum hybrid composites were fabricated using the infiltration method. Then, the composites were extruded to evaluate changes in its mechanical properties. In addition, the dispersion of reinforcements was investigated using a hardness test. The required extrusion pressure of hybrid MMCs increased as the Al₂O₃/CNT fraction increased. The deformation resistance of hybrid material was over two times that of the original A356 aluminum alloy material due to strengthening by the Al₂O₃/CNTs reinforcements. In addition, an unusual trend was detected; primary transition was induced by the hybrid reinforcements, as can be observed in the pressure–displacement curve. Increasing temperature of the material can help increase formability. In particular, temperatures under 623 K (350 °C) and over-incorporating reinforcements (Al₂O₃ 20 pct, CNTs 3 pct) are not recommended owing to a significant increase in the brittleness of the hybrid material.     

赤藓糖醇/碳纳米管复合相变材料热特性模拟研究

在“碳达峰、碳中和”的大背景下,能源结构从一次能源向新能源转变刻不容缓。由于新能源具有间歇性、波动性的特点,储能技术可以有效解决上述问题而得到了广泛的关注。相变材料作为储能技术的关键,其热导率低的问题亟需解决。赤藓糖醇作为中低温区常用的高焓值相变材料,热导率仅为0.7 W?m–1?K–1,严重制约了实际应用中的能量利用效率。本文以赤藓糖醇作为主要研究对象,采用具有超高导热系数的单壁碳纳米管作为导热增强材料,借助分子动力学模拟的方法探究了碳纳米管长度、质量分数以及分布方式对赤藓糖醇/碳纳米管复合相变材料热导率的影响规律。当碳纳米管轴向长度小于其声子平均自由程时,复合相变材料热导率随碳纳米管轴向长度增加而增大,同时随碳纳米管质量分数增加而增大,但表现出显著的各向异性。由于引入赤藓糖醇–碳纳米管界面,复合相变材料径向热导率相比纯赤藓糖醇反而降低。当碳纳米管在赤藓糖醇中随机分布时,热导率的各向异性得到了显著改善且各方向热导率均得到了提升。通过对比复合前后赤藓糖醇与碳纳米管的声子振动态密度发现,由于两者间的相互作用,碳纳米管的声子振动受到抑制,而赤藓糖醇中声子热输运得到激发,从而提高了热导率。      

镀钨碳纳米管增强镁基复合材料的摩擦磨损性能研究

以羰基钨为前驱体, 采用金属有机化学气相沉积在碳纳米管表面镀覆了金属钨, 利用磁力搅拌混粉和放电等离子体烧结制备了镀钨碳纳米管增强镁基复合材料((W-CNTs) /Mg), 研究了W-CNTs质量分数对复合材料摩擦磨损性能的影响。结果表明: W-CNTs的加入可对镁基体起到降低摩擦系数、减少磨损量的作用; 当W-CNTs质量分数为0.75%时, 复合材料的摩擦系数和磨损量均最小, 分别较纯镁降低了43.7%和71.4%;增加或降低复合材料中的W-CNTs质量分数, 材料的摩擦系数、磨损量均将增大。(W-CNTs) /Mg复合材料的摩擦磨损性能高于CNTs/Mg复合材料。     

Methanol Oxidation over TiO2-modified Multi-walled Carbon Nanotubes Supported Pt-Mo Electrocatalyst

In order to develop a novel and high-performance catalytic material for direct methanol fuel celIs(DMFC), molybdenum oxide as a co-catalyst with Pt on multi-walled carbon nanotubes which were modified by titanium dio- xide(denoted as CNTs@TiO<,2>) was investigated. The physicochemical characterizations of the catalysts were carried out via X-ray diffraction(XRD), transmission electron microscopy(TEM) and X-ray photoelectron spectroscopy(XPS). Cyclic voltammetry(CV) showed that the CO-tolerance performance increased in the sequence of Pt/CNTs< Pt/CNTs@TiO<,2>. The improved CO-tolerance performance of the Pt-Mo/CNTs@TiO<,2> catalyst can be attributed to the combined beneficial effects of highly dispersed Pt nanoparticles on the CNTs, the existence of oxygen holes in the MoO<,3> layer structure and the oxidation capability of TiO<,2>.     

铜改性碳纳米管增强银基复合材料的力学性能和摩擦磨损性能

分别添加2%(体积分数)的多壁碳纳米管(carbon nanotubes,CNTs)和表面镀Cu改性后的碳纳米管(Cu@CNTs)作为增强相,采用热压法制备Ag基复合材料,研究CNTs的表面改性对银基复合材料力学性能和摩擦磨损性能的影响。结果表明,Ag-2Cu@CNTs复合材料中的CNTs团簇减少,由内到外形成Ag到Cu再到CNTs逐层包裹的结构,力学性能优异,硬度(HV)达到105.6,抗拉强度为248.5 MPa,比纯银分别提高30.05%和127.98%;与纯银相比,Ag-2Cu@CNTs材料具有优良的摩擦磨损性能,平均摩擦因数由0.86降至0.28,体积磨损率从88.54×10^?4 mm³/(N·m)降至3.96×10^?4 mm³/(N·m)。     

Effect of rare earth and other cationic promoters on properties of CoMoN_x/CNTs catalysts for ammonia decomposition

Carbon nanotubes(CNTs)supported Co-Mo nitride catalysts were prepared by incipient-wetness impregnation method and temperature-programmed reaction in N2-H2 mixed gases.The effects of cationic promoters(K,Ba,La,Ce and Zr)on the catalytic performance and surface properties were investigated.All samples were characterized by N2 physical adsorption,X-ray diffraction,and temperature-programmed reduction of H2.The results showed that the addition of promoters reduced the crystallite size of Mo2N and Co3Mo3N species and increased their surface area and dispersion.Among the catalysts,the La promoted CoMoNx/CNTs catalyst had the highest ammonia conversion which could reach 97.63% at 600 oC.     

壳聚糖-多壁碳纳米管修饰玻碳电极差分脉冲溶出伏安法测定痕量钯

将多壁碳纳米管(MWCNT)分散于壳聚糖（CTS）溶液中,修饰在玻碳电极（GCE）表面,制成了壳聚糖-多壁碳纳米管修饰玻碳电极(CTS-MWCNT-GCE)。利用差分脉冲溶出伏安法研究了钯在该电极上的溶出伏安特性,优化了试验条件,提出了一种测定痕量钯的新方法。试验发现,在0.1 mol/L乙酸钠-0.1 mol/L盐酸缓冲溶液（pH 4.10）中,钯于－400 mV处被富集在该修饰电极表面,在-300 mV～400 mV电位范围内,以100 mV/s的速率扫描,钯在135 mV（vs. SCE）处出现一灵敏的溶出峰,峰电流与钯的浓度在1.88×10-9～1.69×10-8 mol/L范围内呈良好的线性关系,检出限为3.10×10-10 mol/L。该修饰电极具有良好的稳定性和重复性,在含有1.0×10-9 mol/L钯的溶液中,连续11次测定,其相对标准偏差(RSD)为0.21 %。方法用于矿样中痕量钯的测定,测定结果同火焰原子吸收光谱法（FAAS）的测定结果基本一致。     

纳米碳管铝基复合材料组织与性能的研究

试验采用搅拌铸造法制备了纳米碳管增强铝基复合材料,对其显微组织、硬度、抗拉强度和电阻率进行了研究.结果表明:纳米碳管的加入能够细化复合材料晶粒,表面镀铜后可以抑制基体与增强体之间的界面反应,避免脆性碳化物的生成;复合材料的硬度和抗拉强度随着纳米碳管加入量的增加先增加后减小,纳米碳管的质量分数为1.0%时,达到最大值,与基体相比分别增加了34.8%和34.4%;纳米碳管的加入对基体的导电性影响不大.