氧化石墨烯纳米带杂化粒子和石墨烯纳米带的研究进展

氧化石墨烯纳米带杂化粒子是将氧化石墨烯纳米带(GONRs)与其他纳米粒子经π-π键、氢键等结合方式复合在一起,通过这种特殊的结合形态一方面可以有效地防止GONRs的聚积,另一方面新的纳米粒子的引入能够赋予该杂化材料某些特殊的性能,从而有利于充分发挥GONRs杂化材料在聚合物改性等领域的综合性能。本文综述了氧化石墨烯纳米带杂化粒子的制备方法、性能和应用现状。此外,针对GONRs的还原产物石墨烯纳米带(GNRs)的结构、性能、制备方法及其应用领域也进行了系统性地论述。相关研究表明,氧化石墨烯纳米带杂化粒子的设计与制备是氧化石墨烯纳米带迈向实用领域的一个有效途径,而石墨烯纳米作为石墨烯的一种特殊结构的二维变体,继承了石墨烯优良的导电和导热等性能,同时特殊的边缘效应,因而呈现出了更广阔的应用潜力。     

Au纳米粒子/双层TiO2周期结构的制备及其对乙醇的电催化性质

利用二次阳极氧化法成功制备了双层TiO₂纳米管周期结构。通过改变氧化电压可以有效地调整双层TiO₂纳米管的管径, 从而控制样品的形貌。通过实验优化确定双层TiO₂周期结构的制备条件为一次氧化电压60 V, 二次氧化电压40 V。利用原位光还原法, 在TiO₂周期结构表面负载了Au纳米粒子并研究了前驱体溶液浓度与光照时间对样品的影响。在0.05 mmol/L HAuCl₄溶液中光照90 min后得到的Au纳米粒子具有最优的形貌与分布。这种绿色的原位光还原法因为避免使用保护剂与还原剂而有效提高了Au纳米粒子的催化活性。制备所得的Au/TiO₂周期异质结构可以直接作为工作电极用于乙醇的电催化氧化, 并表现出了良好的催化活性与稳定性。除了Au纳米粒子, 其他金属纳米粒子如Ag、Pd、Cu等均可通过该方法成功负载于双层TiO₂纳米管周期结构上。这种新型的异质结纳米结构作为燃料电池的阳极材料表现出了巨大的潜力。     

Pd-Sn-Co纳米粒子修饰还原氧化石墨烯/CuBi2O4复合材料的制备及电催化性能

采用水热-浸渍还原法将Pd-Sn-Co纳米粒子固载到氧化石墨烯（GO）/CuBi₂O₄载体上,成功获得Pd-Sn-Co@还原氧化石墨烯(rGO)/CuBi₂O₄复合催化剂,并用于碱性介质中乙二醇的电催化氧化。通过比较单金属Pd、双金属Pd-Co、Pd-Sn及三金属Pd-Sn-Co@rGO/CuBi₂O₄四种负载型催化剂的电催化性能发现,三金属Pd-Sn-Co@rGO/CuBi₂O₄展现出最高的电催化活性和抗毒能力,其正向峰电流密度达到186.54 mA·cm?2,是商用Pd/C (29.57 mA·cm?2)的6.3倍。这种优良的电氧化性能归功于载体GO/CuBi₂O₄独特的三维结构为负载金属提供了充足的界面和活性位点及良好分散性的Pd-Sn-Co三金属纳米粒子之间强烈的协同作用,此外,将GO引入到CuBi₂O₄中有利于多金属纳米粒子的负载并吸附更多的含氧物种,提供优良的电子转移并增大与乙二醇分子的接触面积。这种新型复合材料的制备为发展高效Pd基电催化氧化直接醇类燃料电池提供了新途径,具有较好的理论和应用价值。      

纳米铁氧化过程中的尺寸和压力效应

利用氢电弧等离子体方法制备出纳米铁超微粒子，半退火后的铁钠米粒子，一般铁粉以及由示经处理的纳米粒子压结成的固体材料氧化，通透射电镜观察退火后粒子粒径变化，利用射线衍射分析其氧化产物。     

氧化物包覆金属复合纳米粒子的形成机制及稳定性研究

在传统的“汽-液-固（VLS）”生长机制的基础上，提出了“定量氧辅助汽-液-固（SOA—VLS）”生长机制，解释了氧化物包覆金属复合纳米柱子的形成机制和过程，并利用直流电弧等离子体法制备出多种氧化物包覆金属复合纳米粒子，如氧化硅包覆、氧化硼包覆、氧化钛包虔和多种稀土氧化物包覆的金属纳米壳／核结构复合粒子。本文着重介绍了氧化硼包覆金属复合纳米粒子的结构特征，以及温度敏感特性和酸碱腐蚀性。     

强磁靶共溅射法制备具有室温磁电阻特性的Co-TiO2纳米复合薄膜

Co-TiO₂纳米复合薄膜作为一种新型自旋电子材料, 由于具有良好的生物相容性, 近年来受到广泛关注。但在制备过程中, 磁性金属Co处于氧化气氛, 容易部分氧化, 从而影响薄膜的隧道磁电阻性能。为了抑制磁性金属的氧化, 提高金属态含量, 本研究通过强磁靶共溅射法制备了Co-TiO₂纳米复合薄膜。该方法采用的强磁靶头, 磁场强度高、分布均匀, 可以提高溅射粒子的能量和溅射速率, 降低因高能粒子碰撞而发生氧化的概率。因此强磁靶共溅射法能明显抑制金属Co的氧化, 提高纳米复合薄膜的自旋极化率。所制备的Co-TiO₂纳米复合薄膜主要由非晶态的TiO₂基体和分散其中的Co颗粒组成。通过调节金属Co颗粒尺寸和分布状态, 在电学上实现了金属态向绝缘态转变, 在磁学上实现了铁磁性向超顺磁性转变。Co含量为51.3at%时, Co-TiO₂纳米复合薄膜表现为高金属态和高电阻率, 并且实现了高达8.25%的室温隧道磁电阻。强磁靶共溅射法使Co-TiO₂纳米复合薄膜的室温磁电阻性能得到了进一步提高, 这对于磁性金属—氧化物纳米复合薄膜的研究有着重要的意义。     

真空烧结对纳米铜粒子性能的影响

用TEM、XRD等方法研究了蒸发法制备的纳米铜粒子真空烧结后粒子尺寸及晶相的变化。将烧结处理后的铜粒子负载于低温氧化铝上,考察了对CO氧化反应的催化活性。结果表明,随处理温度的增加,纳米铜粒子烧结程度增加,尺寸变大,催化活性下降,晶相也由Cu、CuO变为Cu2O。     

Ni-Sn金属间化合物纳米粒子的制备和热稳定性

采用直流电弧放电法制备Ni-Sn纳米粒子,研究了纳米粒子的结构、成份、形貌和热稳定性.结果表明,Sn 比Ni蒸发得快是纳米粒子的成份与原料明显偏差的主要原因.由于非平衡反应和极短的反应时间,得到的是含有Ni3Sn4的多相混合物.与低熔点的Sn纳米粒子比较,Ni-Sn金属间化合物纳米粒子在725 K左右氧化缓慢,具有良好的热稳定性.     

高性能磁性液体材料研究进展

解决纳米磁性粒子的耐氧化问题对制备高性能磁性液体具有重要意义。系统介绍了金属磁性液体和氮化铁磁性液体的制备方法，并对各种制备方法进行了评述。综述了磁性液体的耐氧化研究进展，主要是纳米金属粒子的无机物包覆和氮化铁磁性液体的抗氧化剂添加；展望了高性能磁性液体在耐氧化方面的研究趋势。     

聚合物包覆金属纳米粒子的制备研究进展

近年来,金属纳米粒子,尤其是金、银和铜,由于独特的热学、光学和电学性质及在纳米电子、纳米光学、信息存储、催化、生物和生物医学方面的潜在应用吸引了重大的研究兴趣。目前,聚合物包覆金属纳米复合粒子的研究得到广泛关注。一方面可以保持金属纳米粒子的特殊性质和功能,另一方面聚合物作为壳层材料可以增强纳米粒子的长期稳定性,调控纳米粒子的溶解性,提高纳米粒子与聚合物基体的相容性和可加工性等。本文综述了聚合物包覆金属纳米粒子的制备研究进展,主要包括乳液聚合法、沉淀聚合法、原位聚合法、配体交换法、壳交联法等,提出和分析了每种方法的优缺点,并对该材料的发展做了展望。聚合物包覆金属纳米粒子的工业化应用仍然是一个重要的挑战,有待进一步发展更适合工业化生产的方法。     

Optical currents in vector fields

We present the results of computer simulation of the spatial distribution of the Poynting vector and illustrate motion of microparticles and nanoparticles in spatially inhomogeneously polarized fields. The influence of phase relations and the degree of mutual coherence of superimposing waves on the characteristics of the microparticle's motion has been analyzed. For the first time, we have shown experimentally the possibility of diagnostics of optical currents in liquids caused by polarization characteristics of an optical field alone, using test metallic particles of nanoscale.     

Fabrication of nanoscale rings, dots, and rods by combining shadow nanosphere lithography and annealed polystyrene nanosphere masks

The application of shadow nanosphere lithography for the preparation of large-area, two-dimensional, metallic nanostructures of different shape is described. Through changing the mask morphology by temperature processing and varying the evaporation conditions, particles with morphologies such as rings, rods, and dots have been produced. This process allows outstanding control of the size and morphology of the particles. The efficient technique is shown to scale down the size of metallic nanoparticles from 200 to 30 nm, while preserving the original nanosphere spacing and order. The 150-nm-diameter Fe rings produced by this method show ferromagnetic behavior, which was predicted by theoretical simulation. All the experimental results were confirmed by computer simulations, which also showed the possibility of creating periodic arrays of any other geometrical shape.     

Preparation of Benzene-Stabilized Aluminum Nanoparticles in Hydrogen Atmosphere

Benzene was shown to be a suitable organic matrix for stabilizing Al nanoparticles. The clustering and motion of evaporated atoms were studied by computer simulations using a Monte Carlo procedure. The emission spectra of metallic Mg, Ca, Cd, and Zn were measured during evaporation in atomic hydrogen atmosphere. The thermal effect of hydrogen recombination was found to notably reduce the evaporation temperature. Electron-microscopic examination showed that the benzene layer thickness had a significant effect on the particle size and aggregation of the deposited Al. IR spectroscopic studies revealed the formation of an aluminum compound with benzene.     

Atomistic simulation and modeling of localized shear deformation in metallic glasses

Since the end of 1980s, bulk metallic glasses became available for various multi-component alloys. Because bulk metallic glasses are applicable to structural materials, their mechanical properties have become a matter of great interest in these decades. A characteristic feature of plastic deformation of metallic glasses at the ambient temperature is the localized shear deformation. Since we have no appropriate experimental technique, unlike crystalline matter, to approach microscopic deformation process in amorphous materials, we have to rely on computer simulation studies by use of atomistic models to reveal the microscopic deformation processes. In this article, we review atomistic simulation studies of deformation processes in metallic glasses, i.e., local shear transformation (LST), structural characterization of the local shear transformation zones (STZs), deformation-induced softening, shear band formation and its development, by use of elemental and metal-metal alloy models. We also review representative microscopic models so far proposed for the deformation mechanism: early dislocation model, Spaepen’s free-volume model, Argons’s STZ model and recent two-state STZ models by Langer et al.     

Fate and toxicity of metallic and metal-containing nanoparticles for biomedical applications

It is important to obtain a better understanding of the uptake, trafficking, pharmacokinetics, clearance, and role of nanomaterials in biological systems, so that their possible undesirable effects can be avoided. A number of metallic or metal-containing nanomaterials, such as gold nanoparticles and nanorods, quantum dots, iron oxides nanoparticles, and endohedral metallofullerenes, have already been or will soon become very promising for biomedical applications. This review presents a summary of currently available data on the fate and toxicity of these metallic or metal-containing nanoparticles based on animal studies. Several issues regarding the nanotoxicity assessment and future directions on the study of the fate of these nanoparticles are also proposed.     

Cr20Ni80电热合金电渣重熔数值模拟

采用ANSYS软件中的热电耦合单元,研究了电渣重熔过程中熔铸电流、冷却系数及渣池深度对金属熔池温度分布的影响。采用ProCAST软件中的CAFE模块模拟了铸锭的微观组织,并将模拟结果与实际实验的微观组织进行了对比。结果表明:随着电流的增加整体温度逐渐上升;随着冷却系数以及渣池深度的增加,熔池温度逐渐降低,熔池深度逐渐变浅。实际生产与软件模拟的Cr20Ni80电热合金组织都由表层细晶区、柱状晶区以及等轴晶区3部分组成,且晶粒大小相近,说明模拟结果与实验结果具有一定的吻合性。     

Nonlinear and magneto-optical transmission studies on magnetic nanofluids of non-interacting metallic nickel nanoparticles

Oxide free stable metallic nanofluids have the potential for various applications such as in thermal management and inkjet printing apart from being a candidate system for fundamental studies. A stable suspension of nickel nanoparticles of ～ 5 nm size has been realized by a modified two-step synthesis route. Structural characterization by x-ray diffraction and transmission electron microscopy shows that the nanoparticles are metallic and are phase pure. The nanoparticles exhibited superparamagnetic properties. The magneto-optical transmission properties of the nickel nanofluid (Ni-F) were investigated by linear optical dichroism measurements. The magnetic field dependent light transmission studies exhibited a polarization dependent optical absorption, known as optical dichroism, indicating that the nanoparticles suspended in the fluid are non-interacting and superparamagnetic in nature. The nonlinear optical limiting properties of Ni-F under high input optical fluence were then analyzed by an open aperture z-scan technique. The Ni-F exhibits a saturable absorption at moderate laser intensities while effective two-photon absorption is evident at higher intensities. The Ni-F appears to be a unique material for various optical devices such as field modulated gratings and optical switches which can be controlled by an external magnetic field.     

封闭腔内纳米流体自然对流换热的数值模拟

采用数值模拟方式研究充满了纳米流体的封闭腔内的稳态自然对流。重点分析了纳米颗粒的体积分数,Ra数以及不同类型纳米颗粒对自然对流换热特性的影响。数值模拟结果表明:在纯水中加入纳米颗粒可以显著提高基液的自然对流换热特性;对于给定的Ra数下,随着纳米流体的体积分数增大,纳米流体换热效果显著增强;对于给定的体积分数下,随着Ra数增大,纳米流体的换热强度也随之增大,并且换热机理由热传导为主变为热对流为主;通过Ag,Cu,CuO和Al2O3四种纳米颗粒的对流换热效果比较分析得出,金属Ag和Cu纳米颗粒比金属氧化物CuO和Al2O3的纳米颗粒制备的纳米流体的对流换热效果更好。     

Control of cluster coalescence during formation of bimetallic nanoparticles and nanoalloys obtained via electric explosion of two wires

In this study, the possibility of controlling the coalescence of clusters during the formation of bimetallic nanoparticles and nanoalloys is demonstrated for the first time using joint electric explosion of Nb/Al and Nb/Ag wires under an argon atmosphere as an example. The evolution of clusters in the condensed phase is considered based on the adiabatic approximation to expand the products of the electric explosion of wires. Controlling the temperature and size of the clusters formed under the electric explosion of wires generating the energy necessary for the transition from the metallic state to the two-phase state (clusters of the condensed phase and weakly ionized plasma) allows synthesizing nanoparticles and bimetallic nanoparticles possessing the structures of nanoalloys and Janus particles, respectively. The experimental studies are supplemented by describing structural patterns and segregation phenomena using a hybrid computer experiment that adopts two alternative methods, i.e., the Monte Carlo and molecular dynamics methods. Both methods predict similar structure formation trends, particularly segregation patterns, in Nb–Ag and Nb–Al nanoparticles. For the first time, we have obtained bimetallic nanoparticles possessing a more complex structure, compared to the formerly known core shell, namely the onion-like structure. The Nb₂₉₆₄–Ag₂₉₆₄ and Nb₂₉₆₄–Al₂₉₆₄ nanoparticles s are characterized by the formation of icosahedral cores and crystalline cores based on the hcp and fcc phases, respectively, over the entire temperature range studied.     

Synthesis of metallic nanoparticles protected with N,N,N-trimethyl chitosan chloride via a relatively weak affinity

A water-soluble cationic chitosan derivative, N,N,N-trimethyl chitosan chloride (TMC), was synthesized and used as a stabilizing reagent for the synthesis of highly stable Au, Ag and Pt nanoparticles in a single-phase of neutral aqueous solution. The morphology and stability of metallic nanoparticles were evaluated by transmission electron microscopy and UV-vis spectroscopy. The results showed that well-dispersed metallic nanoparticles have a spherical morphology with diameters of about 3 ± 0.5?nm. The prepared gold nanoparticles are stable in the aqueous solution (no significant changes in their morphology and size within 10?months) due to repulsion between the charged polymer shell coatings around the metallic nanoparticles. The relatively low affinity of TMC on gold nanoparticles was confirmed by using a ligand exchange experiment. The mechanism stabilizing the chitosan derivative and the neighbouring gold nanoparticles was identified by FTIR, (1)H NMR and (13)C NMR measurements.