包覆型铜-银双金属粉的制备

为了提高铜粉的抗氧化性能,在超细铜粉表面包覆一层具有优良导电性和抗氧化的银,以乙酰丙酮(Acac)为Cu2+的螯合剂,采用置换反应法制备与原超细铜粉粒度相同的包覆型铜-银双金属粉.采用X射线衍射仪(XRD)、煅烧后增重等手段分析包覆型铜-银双金属粉的抗氧化性能,并用扫描电子显微镜(SEM)表征了其表面形貌.结果表明,乙...     

化学镀法制备核壳型银-铜双金属粉

为改善超细铜粉的高温抗氧化性能,通过热力学数据理论上分析了液相还原反应取代置换反应的可行性,并以水合肼作还原剂,银以稳定性适中的银氨络合物存在,采用化学镀法制备银包覆超细铜粉的新技术,利用SEM、XRD等手段对双金属粉的形貌和晶相组成进行了分析.研究表明,一次包覆铜粉基体表面银的包覆率为40.22%,二次包覆银的包覆率可达94.98%,在铜粉表面形成了连续的银膜,可以认为是表面包覆结构,拓展了超细铜粉的应用领域.     

化学还原法制备核壳铜-银包覆粉的研究进展

由于其良好的抗氧化性、热稳定性及高电导性,核壳结构铜-银包覆粉在电子浆料、导电填料等众多领域具有广阔的应用前景.总结归纳了化学还原法制备核壳结构铜-银包覆粉的研究进展,重点介绍了直接置换法和还原剂还原两种方法的制备工艺、机理及研究结果.分析表明:包覆过程中铜粉的性能、温度、搅拌速度等因素对最终包覆产品的性能有较大影响;铜粉的氧化、包覆时的水解及银盐利用率低等问题是制约核壳结构铜-银包覆粉制备的关键问题.据此提出了相应的解决措施,并对今后的研究应用方向进行了展望,为进一步深入研究奠定了基础.     

化学镀法制备纳米Cu/Al复合粉末

为了改善超细铝粉的表面易氧化问题和微米级铝粉对推进剂的热分解催化作用不明显现象,以对推进剂具有良好催化作用的纳米Cu包覆金属Al表面.采用化学镀铜法对微米级铝粉表面进行镀覆,制备出纳米Cu粒子在超细Al颗粒表面包覆完整的Al-Cu核壳式复合粉末,并利用正交实验优化镀液组分及镀覆工艺条件.利用XRD、SEM、EDX等仪器,对复合粉末的形貌、物相结构及表面成分进行分析,结果表明铝粉表面包覆一层致密的纳米铜层,这种纳米层是由粒度约为18.83nm的晶态析出的纳米铜组成.     

NiO包覆Ni纳米颗粒的制备及其氧化特性研究

通过对直流电弧等离子体制备的Ni纳米颗粒钝化处理得到NiO包覆Ni纳米颗粒。并对试样的组成成分、形貌、晶体结构、粒度和氧化特性采用高分辨透射电子显微镜(HRTEM)、X射线衍射(XRD)、透射电子显微镜(TEM)和选区电子衍射(SAED)、热重和差示扫描量热分析仪(TGA/DSC)等手段进行分析。结果表明:经过表面钝化处理的NiO包覆Ni纳米颗粒具有明显的核-壳结构,内核为纳米Ni,外壳为NiO氧化物。颗粒呈球形,粒度均匀,分散性良好,粒径分布在20~70nm范围内,平均粒径为44nm,壳层氧化膜的厚度为5~8nm。壳核结构防止了纳米Ni颗粒的进一步氧化和团聚。     

纳米铜粉与碳包覆铜纳米粉的分散性能比较

采用直流碳弧法制备平均粒径为25 nm的碳包覆铜纳米粉,应用X射线衍射(XRD)、透射电镜(TEM)等分析手段对所制备的纳米颗粒物相、形貌等进行表征。采用超声波分散法对所制备的碳包覆铜纳米粉和市售的纳米铜粉进行分散,并通过分光光度法和沉降实验对两者的分散性能进行比较。结果表明:铜纳米颗粒具有很高的表面自由能,容易被氧化,在水性液相介质中分散时容易产生氢氧化铜絮状沉淀。碳包覆铜纳米颗粒表面有碳层的保护,且密度小、表面吸附性能好,分散性能明显优于铜纳米颗粒。     

微纳级银包铜颗粒的快速制备及其导电性能

提出一种制备银包铜(Cu-Ag)核壳颗粒的一步化学置换法。使用成本较低的柠檬酸三纳(SC)作为还原剂和螯合剂,用明胶(Gelatin)作为分散剂,硫酸银(Ag_2SO_4)为Ag源,用一步化学置换法制备银包铜(Cu-Ag)核壳颗粒,研究了Ag_2SO_4和SC用量对Cu-Ag颗粒包覆效果和抗氧化性能的影响。结果表明,SC的剂量直接影响表面包裹的Ag颗粒形貌和均匀度。Ag_2SO_4剂量越大则Cu表面的Ag包裹量越大,导电性越好。当SC的剂量为1.5 g,Ag_2SO_4的剂量为8.0 g时Cu-Ag颗粒包覆效果好且电阻较低(仅为1.1Ω),因此可尽量降低Ag的消耗量提高颗粒的导电性。     

核壳结构纳米Ni／Al复合粉末的制备

在含氟离子的水溶液中，采用Al粉直接置换还原Ni盐的方法，实现了纳米Ni在Al粉表面上的快速化学沉积，制备出核壳结构的Ni／Al复合粉末。探讨了反应的过程，利用SEM、XRD、BET等测试手段对复合粉末进行了微观测试和表征。结果表明：Al粉表面连续、均匀包覆了由晶粒大小约20．6nm的Ni纳米颗粒组成的壳层。     

纳米铜润滑油添加剂的制备及其摩擦学性能

为了研究纳米铜粉的制备与其摩擦学性能,利用高能球磨机采用干湿磨相结合的方法制备了纳米铜粉,再将其加入500SN齿轮油中制成润滑油添加剂,用透射电镜(TEM)及万能磨擦磨损试验机研究了纳米铜粉的微观形貌及其润滑油添加剂的摩擦学性能。结果表明:纳米铜粉粒径为10～40 nm,在修饰剂中分散较好,颗粒表面有明显包覆层;纳米铜润滑油添加剂可提高基础油的减摩抗磨性能;纳米铜粉含量0.05%的纳米铜润滑油样的摩擦学性能最好且摩擦系数最低;低载荷下纳米铜润滑油样的摩擦学性能优于高载荷下的。     

消息报道

正合肥物质科学院铜纳米颗粒/石墨烯核壳结构材料催化研究获进展近期,中国科学院合肥物质科学研究院固体物理研究所研究员李越课题组和北京理工大学教授曲良体课题组合作,在核壳结构的纳米材料研究方面取得新进展,研制出构筑尺寸均一的石墨烯包覆铜纳米颗粒核壳结构的复合材料,其催化效率大幅提高,是金纳米颗粒的14倍。相比于单组分材料,由于核与壳的相互耦合,核壳结构的纳米材料(如以金属颗粒为核,无机或有机材料为壳)的部分性能会大幅度提高。以贵金属(铂、金、银等)纳米颗粒为核的核壳材料,被广泛应用于光学、电化学及催化等领域。然而,     

Self-organized bimetallic Ag-Co nanoparticles with tunable localized surface plasmons showing high environmental stability and sensitivity

We demonstrate a promising synthesis route based on pulsed laser dewetting of bilayer films (Ag and Co) to make bimetallic nanoparticle arrays. By combining experiment and theory we establish a parameter space for the independent control of composition and diameter for the bimetallic nanoparticles. As a result, physical properties, such as the localized surface plasmon resonance (LSPR), that depend on particle size and composition can be readily tuned over a wavelength range one order of magnitude greater than for pure Ag nanoparticles. The LSPR detection sensitivity of the bimetallic nanoparticles with narrow size distribution was found to be high-comparable with pure Ag (～60 nm/RIU). Moreover, they showed significantly higher long-term environmental stability over pure Ag.     

Facile synthesis of near-monodisperse Ag@Ni core-shell nanoparticles and their application for catalytic generation of hydrogen

Magnetically recyclable Ag-Ni core-shell nanoparticles have been fabricated via a simple one-pot synthetic route using oleylamine both as solvent and reducing agent and triphenylphosphine as a surfactant. As characterized by transmission electron microscopy (TEM), the as-synthesized Ag-Ni core-shell nanoparticles exhibit a very narrow size distribution with a typical size of 14.9 ± 1.2 nm and a tunable shell thickness. UV-vis absorption spectroscopy study shows that the formation of a Ni shell on Ag core can damp the surface plasmon resonance (SPR) of the Ag core and lead to a red-shifted SPR absorption peak. Magnetic measurement indicates that all the as-synthesized Ag-Ni core-shell nanoparticles are superparamagnetic at room temperature, and their blocking temperatures can be controlled by modulating the shell thickness. The as-synthesized Ag-Ni core-shell nanoparticles exhibit excellent catalytic properties for the generation of H(2) from dehydrogenation of sodium borohydride in aqueous solutions. The hydrogen generation rate of Ag-Ni core-shell nanoparticles is found to be much higher than that of Ag and Ni nanoparticles of a similar size, and the calculated activation energy for hydrogen generation is lower than that of many bimetallic catalysts. The strategy employed here can also be extended to other noble-magnetic metal systems.     

Synthesis and characteristics of Ag/Pt bimetallic nanocomposites by arc-discharge solution plasma processing

Arc discharge in solution, generated by applying a high voltage of unipolar pulsed dc to electrodes of Ag and Pt, was used as a method to form Ag/Pt bimetallic nanocomposites via electrode erosion by the effects of the electric arc at the cathode (Ag rod) and the sputtering at the anode (Pt rod). Ag/Pt bimetallic nanocomposites were formed as colloidal particles dispersed in solution via the reduction of hydrogen radicals generated during discharge without the addition of chemical precursor or reducing agent. At a discharge time of 30?s, the fine bimetallic nanoparticles with a mean particle size of approximately 5?nm were observed by transmission electron microscopy (TEM). With increasing discharge time, the bimetallic nanoparticle size tended to increase by forming an agglomeration. The presence of the relatively small amount of Pt dispersed in the Ag matrix could be observed by the analytical mapping mode of energy-dispersive x-ray spectroscopy and high-resolution TEM. This demonstrated that the synthesized particle was in the form of a nanocomposite. No contamination of other chemical substances was detected by x-ray photoelectron spectroscopy. Hence, solution plasma could be a clean and simple process to effectively synthesize Ag/Pt bimetallic nanocomposites and it is expected to be widely applicable in the preparation of several types of nanoparticle.     

A simple approach for facile synthesis of Ag,anisotropic Au and bimetallic (Ag/Au) nanoparticles using cruciferous vegetable extracts

We present a simple and straightforward approach for the synthesis and stabilization of relatively monodisperse Ag, Au and bimetallic (Ag/Au) nanoparticles by using cruciferous vegetable (green/red) extracts by simply adjusting the pH environment in the aqueous medium. The vegetable extracts act both as reducing and capping agents. The monometallic and bimetallic nanoparticles of Ag and Au so obtained were characterized by UV–visible spectroscopy, X-ray diffraction (XRD), dynamic light scattering (DLS) and transmission electron microscopy (TEM). It is shown that red cabbage extract can be used for the preparation of anisotropic Au nanoparticles. The formation of Au anisotropic nanoparticles was found to depend on a number of environmental factors, such as the pH of the reaction medium, reaction time, and initial reactant concentrations. Additionally, it is shown that these extract-stabilized Au and Ag nanoparticles can be used as a seed for preparation of bimetallic Au/Ag nanoparticles. For bimetallic alloy nanoparticles the absorption peak was observed between the two maxima of the corresponding metallic particles. The surface plasmon absorption maxima for bimetallic nanoparticles changed linearly with increasing Au mole ratio content in various alloy compositions. It has been shown that the formation of hollow Au spheres depends on the experimental conditions.     

Synthesis of highly environmental stable copper–silver core–shell nanoparticles for direct writing flexible electronics

In this study, Cu@Ag core–shell nanoparticles (NPs) with highly environmental stability were synthesized successfully by combining the NaBH₄ reduction method with the transmetallation reaction, and the Cu@Ag nano-ink was prepared for direct writing flexible electronics. The structure, component, thermal stability and oxidation resistance of Cu NPs and Cu@Ag core–shell nanoparticles were characterized and discussed systematically. The results showed that Cu NPs could be obtained via the reduction of Cu²⁺ ions by using cetyltrimethylammonium bromide (CTAB) as a dispersing agent under an excess of sodium hydroxide (NaOH) and sodium borohydride (NaBH₄) in aqueous solution. And the Cu@Ag core–shell nanoparticles with uniform Ag shell and Cu core can be fabricated with the transmetallation reaction that Ag⁺ ions were reduced by the copper atoms on the surface of Cu NPs at pH 7, and the Cu core were kept from oxidation from the Ag shell. Besides, Cu@Ag nano ink were fabricated by dispersing Cu@Ag core–shell nanoparticles in ethylene glycol, and Cu@Ag conductive pattern were directly drawn on ordinary photo paper using a roller pen filled with 30 wt% Cu@Ag nano ink. The electrical resistivity of the conductive Cu@Ag pattern obtained from the nano ink was as low as 13.8 μΩ cm^?1 due to the continuous interconnections between the nanoparticles established when thermal sintered at 150?°C for 1 h under N₂. When the conductive wires of a lamp were connected to the two ends of the written conductive line, the lamp was illuminated immediately. It demonstrated that the complicated Cu@Ag nano-ink pattern had very good conductivity and applicability. This work provides an effective approach to prepare Cu@Ag core–shell nano-ink for direct writing flexible electronics.     

Pulse electrodeposition of Ag,Cu nanoparticles on TiO2 nanoring/nanotube arrays for enhanced photoelectrochemical water splitting

In this paper, plasmonic Ag and Cu nanoparticles were co-deposited on TiO₂ nanoring/nanotube arrays (TiO₂ R/T) by using two-step pulse electrodeposition method for investigating the optical and photoelectrochemical properties, in comparison to monometallic Ag, Cu decoration. By optimizing the electrodeposition cycle times and electrolyte concentration, bimetallic Ag–Cu/TiO₂ R/T-0.5 with moderate densities and sizes of Ag and Cu nanoparticles was fabricated and shows great photocatalytic potential, in which, Ag mainly facilitates the generation of hot electrons by absorbing visible light and Cu plays an important role in accelerating the separation and transportation of hot electrons. The hydrogen production rate was tested as 425 μL h^?1 cm^?2, which is about 1.34-fold enhanced H₂ production over TiO₂ R/T. Furthermore, molecular dynamics simulations were made for analyzing the interface electrostatic properties between plasmonic nanoparticles of Ag or Cu and the semiconductor TiO₂. It is calculated that bimetallic Ag–Cu/TiO₂/H₂O system has larger interfacial Helmholtz potential than monometallic Ag/TiO₂/H₂O, Cu/TiO₂/H₂O and pure TiO₂/H₂O systems, accelerating the four-electron reaction occurring at the semiconductor/electrolyte interface. This research put forward a feasible and simple pulse electrodeposition method to fabricate bimetallic photoanodes for enhanced hydrogen evolution and an important analysis method of semiconductor/ metal/electrolyte interface characteristics.     

Ferromagnetic signal in nanosized Ag particles

A new technique using an inductively coupled plasma reactor equipped with a liquid-nitrogen cooling system was developed to prepare Ag nanoparticles. The magnetic signal from these Ag particles with diameters of 4 nm showed, surprisingly, a signal with combined ferromagnetic and diamagnetic components, in contrast to the signal with only one diamagnetic component from bulk Ag. The same technique was used to prepare the Ag/Cu nanoparticles, which are Ag nanoparticles coated with a Cu layer. Compared to the Ag nanoparticles, these showed a greatly enhanced superparamagnetic signal in addition to the same value of the ferromagnetism. The comparison between the Ag and the Ag/Cu nanoparticles indicated that the ferromagnetic components are a common feature of Ag nanoparticles while the greatly enhanced paramagnetic component of Ag/Cu, which dominates over the background diamagnetic component from the Ag core, is from the outer Cu shell.     

Nanoparticles of Sn3.0Ag0.5Cu alloy synthesized at room temperature with large melting temperature depression

The Sn3.0Ag0.5Cu (wt%) lead-free solder alloy is considered to be one of the most promising alternatives to replace the traditionally used Sn–Pb solders. This alloy composition possesses, however, some weaknesses, mainly as a result of its higher melting temperature compared to the eutectic Sn–Pb solders. Nanoparticles of Sn3.0Ag0.5Cu lead-free solder alloy nanoparticles were prepared by chemical reduction with NaBH₄ as a reducing agent at room temperature. The melting temperature of the synthesized Sn3.0Ag0.5Cu alloy nanoparticles was determined by differential scanning calorimetry (DSC). The results showed that the calorimetric onset melting temperature of the Sn3.0Ag0.5Cu alloy nanoparticles could be as low as 200 °C, which was about 17 °C lower than that of the bulk alloy (217 °C). The field emission scanning electron microscopy (SEM) images of the as-prepared nanoparticles indicated that the major particle size of Sn3.0Ag0.5Cu nanoparticles is smaller than 50 nm. The structure and morphology of the nanoparticles were analyzed with high resolution transmission electron microscopy (HRTEM). The Ag3Sn and Sn phase were observed in the HRTEM images, which was in good agreement with the XRD results. These low melting temperature Sn3.0Ag0.5Cu alloy nanoparticles show a potential to manufacture high quality lead-free solders for electronic products.     

Growth of Fe3O4 whiskers from solid solution nanoparticles of Fe–Cu and Fe–Ag systems produced by DC plasma jet method

Fe–Cu and Fe–Ag binary systems are virtually immiscible for a whole range of composition in equilibrium. In the present study, the nanoparticles of Fe–Cu and Fe–Ag systems were produced by direct current plasma jet method. These produced nanoparticles had mean particle sizes of about 70 nm, and were a mixture of bcc and fcc phases. It was revealed by analytical high-resolution TEM observations that the nanoparticles of Fe–Cu and Fe–Ag systems were supersaturated solid solution. It has been found that numerous whiskers with a particle on their tip grow from these nanoparticles by heating above the temperature of 860 K under an Ar–O₂ atmosphere. The whiskers grow as the result of the phase separation in these solid solutions. The whiskers are composed of a Fe₃O₄ rod and a Cu₂O particle on the tip.