硅基底上铜纳米粒子催化生长碳纤维的研究

采用微波加热法,在单晶硅基底上生长了铜纳米粒子,并以铜纳米粒子为催化剂,乙炔为碳源,氢气为保护气,在管式炉中制备了碳纤维.利用高视频显微仪观察单晶硅片的预处理情况,采用扫描电子显微镜(SEM)观察硅基底上铜纳米粒子的生长情况和碳纤维的形貌特征,并利用能量色散谱仪(EDS)对铜纳米粒子进行成分及元素分布分析.研究表明,采用抛光-腐蚀的硅片预处理方法,可以更高效地得到具有取向性、长径比大的碳纤维.     

聚合物高能球磨技术的研究进展

高能球磨是一种新型的固态加工工艺和纳米制备技术,能够制备许多溶液或熔融方法难以实现的高性能聚合物、聚合物合金以及聚合物/无机纳米复合材料.综述了聚合物高能球磨技术的原理、研究进展及其应用领域,并展望了聚合物高能球磨技术的发展潜力.     

纳米铜导电油墨的制备及其应用

综述了纳米铜粒子的制备方法,即机械球磨法、辐射合成法、物理气相沉积法等物理制备法及化学制备法,探讨了改进纳米铜导电油墨防氧化、低温烧结、导电性能等关键问题,以及纳米铜导电油墨在印刷RFID电子标签、薄膜开关、触摸屏等方面的应用,并提出纳米铜导电油墨未来的研究方向为：抗氧化、低温烧结、多种印刷方式及产品应用等研究。     

石墨烯基磁性纳米复合材料的制备与微波吸收性能研究进展

本文首先概述了石墨烯独特的物理结构和优异的力学、热学、电磁学性能,然后综述了石墨烯基磁性纳米复合材料的制备方法,并分析了其微波吸收机理,最后结合国内外研究现状展望了石墨烯基磁性纳米复合材料制备与微波吸收性能研究的发展方向,指出揭示复合材料的界面结合机制,调控复合材料的微观形貌,探索石墨烯与磁性纳米粒子微波吸收的协同效应将成为今后研究的重点和热点。     

纳米氧化镁制备技术的展望

对几种常见的制备纳米氧化铗的技术进行了详细的介绍和比较,分析了各种工艺存在的问题.液相沉淀法由于原料廉价,工艺简单使其成为最具有工业应用价值的纳米氧化镁制备技术.但该工艺中仍有诸如粒子团聚的机理、降低粒子团聚的手段等问题值得进一步研究.指出,相移、微波等新技术也应引入到纳米氧化镁的制备工艺中来.     

热处理对坡缕石纳米材料制备及表面改性的影响

为使坡缕石矿零维纳米化和表面改性取得理想的效果,对坡缕石粒子进行热处理后在QM-4H球磨机上使用干-湿法制备出零维纳米坡缕石,并用硅烷偶联剂进行表面改性,用TEM对坡缕石纳米粒子尺寸及改性效果进行表征,考察不同温度的热处理对含矿物水较多的坡缕石矿纳米化和表面改性的影响规律,研究表明,热处理后的坡缕石使用干-湿式球磨法制备可以获得较高的纳米化程度,经表面改性后具有较好的分散效果。     

修饰纳米CdS/聚合物的界面相互作用与光学性能

采用微乳液法结合原位表面修饰合成了纳米尺度的硫化镉粒子,采用溶液共混和静态铺膜方法制备了纳米粒子/聚合物复合体系,以研究纳米粒子与聚合物间的界面作用.结果表明,经修饰的纳米CdS粒子比较均匀地分散于聚合物基体内,纳米粒子与聚合物基体间存在较强的相互作用.根据复合体系的紫外-可见吸收光谱和荧光光谱,分析了表面修饰(表面修饰剂种类、表面修饰剂用量等)对纳米粒子的分散以及复合体系界面特性的影响,证实了表面修饰剂具有促进纳米粒子分散和消除粒子表面缺陷的作用.     

制备超顺磁性Fe_3O_4纳米粒子的研究进展

对超顺磁性Fe3O4纳米粒子的制备方法进行总结,目前常用的方法有共沉淀法、水热法、水解法、微乳液法及溶胶-凝胶法,并讨论了这些方法的优缺点,同时提出了制备Fe3O4纳米粒子的一种新方法——微波水热法。这种方法能够在最短的时间内制备出超顺磁性Fe3O4纳米粒子,并且是制备高纯度、小粒径、均匀分散的超顺磁性Fe3O4纳米粒子最佳方法。最后对超顺磁性Fe3O4纳米粒子的应用及其发展趋势做简单的介绍,对其进一步的研究进行展望。     

纯Al纳米晶体材料的力学性能研究

以纯铝粉(99.7%)为原料,采用不同的球磨参数(球料比、球磨时间),利用高能球磨法在室温下制备了具有纳米晶粒的纯Al体材料.通过X射线衍射(XRD)及显微硬度等手段,对不同球磨工艺参数下制备的纯Al体材料的晶粒尺寸及力学性能进行了测试和分析,并对样品的晶粒尺寸与硬度之间的关系进行了深入的探讨.研究发现,所制备的纯Al纳米晶体材料的平均晶粒尺寸在47～66nm范围内;随着球磨时间的延长,样品的显微硬度呈现出先升高后降低再升高的趋势,并在球磨时间为5h时,球磨样品的硬度达到最高值;屈服强度与晶粒尺寸之间符合正的Hall-Petch关系.     

机械球磨法在纳米储氢材料制备中的应用

机械球磨法是纳米储氢材料制备和加工的重要方法之一。通过机械球磨法制备的材料具有纳米化、合金化和非晶化等优良特性,储氢材料的动力学和热力学性能得到改善。机械球磨法操作工艺简单、成本低、效率高,使其成为制备纳米储氢材料的理想方法之一。简要介绍了机械球磨法的基本原理,重点阐述了机械球磨法在制备纳米储氢材料方面的应用,并对影响机械球磨效果的主要因素进行了分析。对于机械球磨法在制备纳米储氢材料领域的实际应用具有一定的指导意义。     

Processing of Cu-Fe and Cu-Fe-SiC nanocomposites by mechanical alloying

The Cu-Fe and Cu-Fe-SiC nanocomposite powders were synthesized by a two step mechanical alloying process. A supersaturated solid-solution of Cu-20 wt% Fe was prepared by ball milling of elemental powders up to 5 and 20 h and subsequently the SiC powder was added during additional 5 h milling. The dissolution of Fe into Cu matrix and the morphology of powder particles were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. It was found that the iron peaks in the XRD patterns vanish at the early stages of mechanical alloying process but the dissolution of Fe needs more milling time. Moreover, the crystallite size of the matrix decreases with increasing milling time and the crystallite size reaches a plateau with continued milling. In this regard, the addition of SiC was found to be beneficial in postponing the saturation in crystallite size refinement. Moreover, the effect of SiC on the particle size was found to be significant only if it is added at the right time. It was also found that the silicon carbide and iron particles are present after consolidation and are on the order of nanometer sizes.     

Structure characterization of Ag-Ga/poly(methyl methacrylate) nanoparticles

The Ag-Ga/poly(methyl methacrylate) nanoparticles were prepared in-situ by emulsion polymerization method under ultrasonic irradiation without any initiators or metal reductant. HRTEM, EDS and XRD experiments were performed to characterize the nanoparticles. The results indicated that the nanocomposite particles possessed core-shell structure with diameters of 80-200 nm, as well as excellent monodispersity. The phenomenon that the polymer forms the shell via layer-by-layer self-assembly was found. XRD proved the existence of Ag0.72Ga0.28 and the probability of new Ag-Ga alloy because of two unknown diffraction peaks.     

Synthesis of carbon nanostructures by graphite deformation during mechanical milling in air

Abstract

In this investigation, time-dependent carbon nanostructures were prepared by high-energy ball milling in the air from elemental graphite powders. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy (RS), and high-resolution transmission electron microscopy (HRTEM) characterized the ball-milled powders. XRD analysis showed that the crystal size decreased with the milling time. Raman spectra confirmed the presence of carbon nanostructures with sp² hybridization. Meanwhile, HRTEM images revealed different carbon morphologies during the milling time. During the different stages, it appears distortion of layers, large tapes, polyhedral morphologies, nanocapsules, and nano-onions. These carbon nanostructures occur in regions where there is carbon accumulation. In this way, the ball milling process in air conditions can promote distorted carbon and different morphologies.     

Scalable route to mesoporous iron oxides and their Cr(VI) ions uptake capacity study

Here we demonstrate a simple and scalable synthetic route for preparing porous iron oxides with tunable porosity characteristics by using the high-energy mechanical ball milling technique. Nanocomposites composed of networked hematite encapsulated in silica were produced. Silica was utilized as scaffolds to form nanocomposites and then was etched off hydrothermally in a NaOH solution. The formation mechanism of porous iron oxides, effects of volume ratio of silica to magnetite, milling period, calcination temperature and concentration of NaOH solution were studied systematically. The formation process was monitored by applying a variety of techniques, such as scanning and transition electron microscopes (SEM and TEM), and X-Ray diffractometer (XRD). SEM and TEM studies revealed that a jelly-like solid-state nanocomposite of silica and iron oxide was produced after milling process, and networked iron oxide structures encapsulated in silica displayed a high mass contrast and their grain size decreased with elongating milling period. Barrett–Joyner–Halender (BJH) method analysis indicated that the pore width and Brunauer–Emmett–Teller (BET) specific surface area of iron oxide decreased with the increase of milling period and volume ratio of silica to iron oxide, and porosity increased with increasing volume ratio of silica to iron oxide. Magnetic measurement revealed the superparamagnetic nature of the mesoporous materials at room temperature. Further, absorption capacity of Cr (VI) ions onto mesoporous magnetite was checked to evaluate its toxic ions uptake ability.     

Fabrication of Al2O3–20 vol.% Al nanocomposite powders using high energy milling and their sinterability

In this study, alumina-based matrix nanocomposite powders reinforced with Al particles were fabricated and investigated. The sinterability of the prepared nanocomposite powder at different firing temperature was also conducted. Their mechanical properties in terms of hardness and toughness were tested. Alumina and aluminum powder mixtures were milled in a planetary ball mill for various times up to 30 h in order to produce Al₂O₃–20% Al nanocomposite. The phase composition, morphological and microstructural changes during mechanical milling of the nanocomposite particles were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM) techniques, respectively. The crystallite size and internal strain were evaluated by XRD patterns using Scherrer methods.A uniform distribution of the Al reinforcement in the Al₂O₃ matrix was successfully obtained after milling the powders. The results revealed that there was no any sign of phase changes during the milling. The crystal size decreased with the prolongation of milling times, while the internal strain increased. A simple model is presented to illustrate the mechanical alloying of a ductile–brittle component system. A competition between the cold welding mechanism and the fracturing mechanism were found during powder milling and finally the above two mechanisms reached an equilibrium. The maximum relative density was obtained at 1500 °C. The harness of the sintered composite was decreased while the fracture toughness was improved after addition Al into alumina.     

Preparation of Al2O3–TiB2 nanocomposite powder by mechanochemical reaction between Al,B2O3 and Ti

Mechanochemical processing is a novel technique for the synthesis of nano-sized materials. This research is based on the production of Al₂O₃–TiB₂ nanocomposite powder using mechanochemical processing. For this purpose, a mixture of aluminum, titanium and boron oxide powders was subjected to high energy ball milling. The structural evaluation of powder particles after different milling times was conducted by X-ray diffractometry (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results showed that during ball milling the Al/B₂O₃/Ti reacted with a combustion mode producing Al₂O₃–TiB₂ nanocomposite. In the final stage of milling, the crystallite sizes of Al₂O₃ and TiB₂ were estimated to be less than 50 nm.     

纳米相复合Al-Sn合金的反应球磨制备及性能研究

利用反应球磨制备Al-SnO_2-MgH_2粉末,然后通过压制和烧结制备出高热稳纳米相复合结构Al-Sn合金。运用X射线衍射仪(XRD)和扫描电镜(SEM)等研究反应球磨制备的纳米相复合Al-Sn合金的组织和性能。结果表明:采用两步法和添加MgH_2组元的方式所制备的机械合金化(MA)Al-SnO_2-MgH_2复合粉末,经压制和600℃烧结,合金中的SnO_2几乎全部被还原成单质Sn,并呈现双尺度结构。其中,共生反应形成的纳米级Sn粒子和Al_2O_3颗粒均匀弥散地分布在Al基体中,显著提高了合金的硬度,从而使合金表现出低的摩擦系数和磨损量。     

多重结构Ti-B4C/Al2024复合材料的组织和力学性能

为了研究多重结构对铝基复合材料力学性能的影响,将气雾化态Al2024合金粉末与球磨不同时间的Ti-10%(质量分数,下同)B_4C复合粉末混合,采用热压烧结和热挤压的方法制备多重结构Ti-B_4C/Al2024复合材料。通过X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)和拉伸试验机对不同材料的显微组织与力学性能进行观察和测试,并对多重结构复合材料的强韧化行为进行讨论。结果表明:Ti-B_4C/Al2024复合材料多重结构包括基体Al2024、核壳结构Ti/Al₁₈Ti_2Mg_3组织和B_4C颗粒。向Al2024中加入5%预先球磨6h后的Ti-B_4C粉末时,其屈服强度从107MPa提高到122MPa,并且表现出与热挤压Al2024合金几乎相同的伸长率。当球磨时间延长至12h时,试样5TB-12h的伸长率可达到16.4%。然而,复合材料的伸长率随着Ti-B_4C添加量的增加而降低。     

机械球磨制备碳微球及其吸附性能研究

分别以球墨铸铁和石墨为原料,采用机械球磨法成功制备了碳微球.采用XRD、SEM等测试手段对产物进行了形貌分析和结构表征,结果表明,所制备的碳微球产量高,并且以石墨为原料所得产物的颗粒大小均匀、分散性好.对碳微球进行了低温N_2吸附分析,结果表明,产物主要为介孔结构含有少量微孔,且具有较大的比表面积.     

On the mechanism of mechanochemical synthesis of Ti2SC from Ti/FeS2/C mixture

In this study, the synthesis of Ti₂SC MAX phase by high energy ball milling, and the effects of heat treatment on ball milled powder was investigated. To this aim, a mixture of Ti, FeS₂ (as sulfur source), and C according to Ti₂SC stoichiometry, were ball milled by a planetary ball mill for different milling periods up to 10 h. The structural evolution, and the morphology of the products was studied by x-ray diffraction (XRD), and scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS), respectively. The results showed that after 10 h of ball milling, the raw materials reacted together and resulted in the formation of Ti₂SiC and TiC phases. The ball milled powder was then compacted and heat treated at 1000 and 1200 °C. Heat treatment caused the progressing of synthesis reactions, and led to increasing the purity of Ti₂SC phase. The heat-treated powder was leached in 1 M HCl for 2 h to remove iron from the product. The XRD results confirmed successful iron removal by leaching. SEM micrographs of the final product revealed the specific lamellar structure of MAX phases. Elemental mapping confirmed the homogeneous distribution of Ti, S and C elements.