CdS/ZnO复合颗粒的制备与电致发光性能

以sol-gel法制备了ZnO前驱体,并通过水热反应得到了CdS/ZnO复合颗粒.采用红外光谱(IR)、X射线衍射(XRD)、扫描电镜(SEM)表征其结构、组成及形貌,并对其电致发光(EL)特性进行表征.结果表明CdS纳米晶生长在ZnO基体上;EL谱表明没有煅烧的CdS/ZnO复合颗粒表现为CdS的激子发射,发光强度较纯CdS有了明显的提高;而煅烧后的CdS/ZnO复合颗粒则表现为ZnO的缺陷发射,发光谱的半高宽较纯ZnO有所减小.     

Synthesis of CuS and PbS nanocrystals on the basis of PE/NBR polymer/elastomeric composites for their applications

In this research work, we have presented a chemical method to elaborate the PbS, CuS nanocrystals embedded in a polymer composites matrix. We have used polyethylene and nitrile butadiene rubber PE/NBR as a support for synthesis of lead sulfide (PbS) and copper sulfide (CuS) nanocrystals. The size control and morphology of these (PbS and CuS) nanoparticles have been applied by the method of “layer by layer”. The obtained nanoparticles were characterized by X-ray diffraction (XRD), UV–Vis and Atomic Force Microscopy (AFM). UV–Vis spectroscopy was used to determine simple optical responses, getting the biggest transmittances of CuS and PbS nanoparticles. Measured size of CuS nanoparticles is approximately 5.5–90 nm in different dose. X-ray diffraction (XRD) study confirmed the formation of cubic phase of PbS nanocrystals into the composite matrix. The size of PbS was estimated ∼9 nm. The surface morphology and crystallite sizes were determined by Atomic Force Microscopy measurements.     

Bi2S3纳米晶掺杂钠硼硅玻璃的三阶非线性光学性质

利用溶胶-凝胶方法制备了1 wt%Bi2S3纳米晶掺杂钠硼硅玻璃.利用X射线粉末衍射仪(XRD),X射线光电子能谱(XPS),透射电子显微镜(TEM),X射线能量色散谱(EDX),扫描模式透射电子显微镜(STEM)以及高分辨透射电子显微镜(HRTEM)对Bi2S3纳米晶在钠硼硅玻璃中的形貌和微结构进行了表征,同时,利用飞秒Z扫描技术在波长为770 nm对该玻璃的三阶非线性光学性能进行了分析测试.结果表明,尺寸为10～30 nm的Bi2S3正交晶系纳米晶在钠硼硅玻璃中形成,该玻璃的三阶非线性光学折射率γ、三阶非线性吸收率β和三阶非线性极化率χ(3)分别为5.90×10-16 m2/W、7.35×10-9 m/W和4.55×10-18 m2/V2.其中,该玻璃的三阶非线性极化率值比未经掺杂的钠硼硅玻璃(χ(3)=1.09×10-22 m2/V2)高出4个数量级,这表明,随着Bi2S3纳米晶的引入,该玻璃的三阶非线性光学性能将得到显著的提高.     

Three dimensional dendritic morphology and orientation transition induced by high static magnetic field in directionally solidified Al-10 wt.%Zn alloy

Effect of high static magnetic field on the dendritic morphology and growth direction in directionally solidified Al-10 wt.%Zn alloy were studied by three-dimensional (3D) X-ray micro-computed tomography, Electron Back-scattered Diffraction (EBSD) and X-ray Diffraction (XRD). The application of high static axial magnetic field (5T) during directional solidification was found to destabilize the solid/liquid interface and cause the growth direction of dendrite deviate from thermal gradient, leading to irregular solid/liquid interfacial shape and cellular to dendritic morphology transition. The thermoelectric magnetic convection (TEMC) caused by the interaction of thermoelectric effect and magnetic field was supposed to be responsible for the transition. In addition, the EBSD and XRD results confirm that the preferred growth direction of α-Al was found to transform from the traditionally expected <100> to <110>. The dendrite orientation transition (DOT) in Al-10 wt.%Zn alloy can be attributed to the effect of applied magnetic field on the anisotropy of crystal during solidification. The result indicates the potential application of high static magnetic field in altering the morphology and preferred growth direction of dendrite during directional solidification.     

八面体形状的重钼酸钠纳米晶的制备及生长机制

采用热蒸发方法,以红外烧结炉为制备仪器,在玻璃衬底上制备了空心的八面体纳米晶。利用扫描电子显微镜、X射线衍射谱、透射电子显微镜及选区电子衍射分析产物的形貌、尺寸、成分及结构,并对纳米晶的形成机理进行了探讨分析。     

Characterization of Sol-gel-derived TiO2 and TiO2-SiO2 Films for Biomedical Applications

In order to improve the corrosion resistance and biocompatibility of NiTi surgical alloy, TiO2 and TiO2-SiO2 thin films were prepared by sol-gel method. The surface characteristics of the film, which include surface composition, microstructure and surface morphology, were studied by X-ray diffraction (XRD), atomic force microscopy (AFM) and X-ray photoelectron spectra (XPS), respectively. A scratching test was used to assess the interface adhesive strength between the film and substrate. The corrosion resistance of NiTi alloy coated with oxide films were studied by anodic polarization curves measurement in biological solution. Additionally, a preliminary study of the in vitro bioactivity of the films was conducted. The results indicated that TiO2 and TiO2-SiO2 (Ti/Si=4:1) films have higher electrochemical corrosion resistance and can be used as protective layers on NiTi alloy. In addition, TiO2-SiO2 composite films have better bioactivity than TiO2 film.     

Novel In Situ Nanostructure-Dendrite Composites in Zr-Base Multicomponent Alloy System

The evolution of a nanostructure-dendrite composite microstructure of two Zr-base alloys solidified through different casting routes is presented. The alloys were designed by adding different amounts of Nb to the Zr-based multicomponent glass-forming alloy system. The refractory metal Nb promotes the formation of a primary phase having dendritic morphology, whereas the residual melt solidifies to a nanostructured/amorphous matrix. The volume fraction and the morphology of the dendritic phase varied with the Nb content and the adopted casting route. A correlation between the alloy composition and adopted casting method with evolved microstructures and mechanical properties is revealed. These composites exhibit a unique combination of high fracture strength up to 1922 Mpa, as well as plastic strain over 15.8% under uniaxial compression testing at room temperature. The high strength of these composites is imparted by the nanostructured matrix, whereas the large plastic strain is a consequence of the retardation of excessive localized shear banding in the matrix by ductile dendrites. The significant work hardening of the composites prior to fracture is attributed to dislocation multiplication in the solid solution-strengthened dendritic phase.     

Micropattern of nano-hydroxyapatite/silk fibroin composite onto Ti alloy surface via template-assisted electrostatic spray deposition

The surface topography plays an important role in bone formation, which may present specific physical cues to cells and tissues and further improve the bioactivity or osteoconduction of the implants. In this report, nano-hydroxyapatite/silk fibroin (n-HA/SF) composite were prepared via a simplified coprecipitation method. Then these nanocrystals were deposited onto Ti alloy substrates via a template-assisted electrostatic spraying deposition (ESD) technique. The output voltage and flow rate were investigated to produce a cone-jet spraying of n-HA/SF suspensions. By using different types of precisely-designed templates (stripe, grid, and ring), the Ti alloy substrates with different micropatterns (stripe, square, and ring) composed of n-HA/SF composite were created. Our results demonstrated that the precisely-designed micropatterns of n-HA/SF composite onto Ti and its alloy substrates could be easily achieved by using template-assisted ESD.     

The synthesis of composite Sn-SnSb films for lithium-ion batteries by electrochemical deposition

Composite Sn-SnSb nano-crystalline films were fabricated on Cu substrate by an electrochemical deposition process. X-ray diffraction, scanning electron microscopy, and galvanostatic cell cycling were used to characterize the structures and electrochemical properties of the films. The as-deposited films consist of only Sn/SnSb composite nanocrystals with a rather dense morphology. The Sn-SnSb composite electrode gives rise to a very small (6%) initial capacity loss and a rather high specific capacity of about 650 mAh/g, which is significantly higher than the values reported in the literature. The coulombic efficiency during charge-discharge cycles is close to 100%.     

Microemulsion-mediated solvothermal synthesis and morphological evolution of MnCO3 nanocrystals

The morphology- and size-controlled synthesis of MnCO3 nanocrystals was successfully achieved by cationic surfactant-CTAB-microemulsion-mediated solvothermal method. Various comparison experiments with different reactant concentrations and molar ratios between water and CTAB, showed the evolvement law of the morphology and size of the as-synthesized MnCO3 nanocrystals. With slowly increasing the concentration of reactants and/or molar ratio between water and CTAB, the morphology of MnCO3 nanocrystals changed gradually from cube to parallelepiped, and then rhombohedron, whereas the size decreased a little. The effect of the experimental parameters on the shapes and sizes of samples, such as the source of carbonate salts, reaction time, and temperature, were also discussed. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high-resolution transmission electron microscopy (HRTEM) were used to characterize the products.     

碳包Ni纳米晶的形成及其特征

用直流碳弧法制备出碳包Ｎｉ金属纳米晶，在石墨阳极复合棒中掺入不同组份的Ｎｉ，研究其对碳包Ｎｉ纳米，富勒烯等碳微团特性的影响。     

Ce对Mg-5Si合金中初生Mg2Si相变质的影响

利用扫描电子显微镜(SEM)、能量色散光谱仪(EDS)、光学显微镜(OM)、ICP光谱仪及X射线衍射(XRD)等手段研究了Ce对Mg-5Si合金中Mg₂Si相变质的影响。结果表明：添加不同量的Ce使Mg-5Si合金中的初生Mg₂Si相的形貌从粗大的树枝状变为多边形状,共晶Mg₂Si由汉字状变为了细纤维状或点状。Ce的添加量为1.2%时变质效果最佳,初生Mg₂Si 的尺寸从48 μm减小到 9 μm或更小。同时,在1.6% Ce变质的合金中发现了短棒状的Mg-Si-Ce化合物。Ce促进了Mg₂Si的形核,并抑制了Mg₂Si的各向异性生长。     

ZnO micro and nanocrystals with enhanced visible light absorption

In this paper, we investigate the effect of the particle size and morphology on the optical properties of ZnO. A series of ZnO micro and nanocrystals were synthesized by the hydrothermal processing of zinc acetate dihydrate and sodium hydroxide as the starting materials, and polyvinylpyrrolidone (PVP) as the polymer surfactant. The particle size and morphology were tailored by adjusting the reactant molar ratios [Zn²⁺]/[OH⁻], while the reaction temperature and the time remained unchanged. X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and high-resolution TEM (HRTEM) have shown that the micro and nanocrystals have a high crystalline pure wurtzite-type hexagonal structure with nanosized crystallites. The size and morphology of the ZnO micro and nanocrystals were investigated by field emission scanning electron microscopy (FE-SEM), which showed a modification from micro-rods via hexagonal-faceted prismatic morphology to nanospheres, caused by simple adjustment of the reactant molar ratio [Zn²⁺]/[OH⁻] from 1:1 to 1:5. The optical properties of the ZnO micro and nanocrystals, as well as their dependence on the particle size and morphology were investigated by Raman and ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy (DRS). The UV–vis spectra showed that the modification of the particle size and morphology from nanospheres to micro-rods resulted in increased absorption, and a slight red-shift of the absorption edge (0.06 eV). Besides, the band gap energy of the synthesized ZnO micro and nanocrystals showed the red shift (∼0.20 eV) compared to bulk ZnO. According to the results of a Raman spectroscopy, the enhanced visible light absorption of the ZnO micro and nanocrystals is related to two phenomena: (1) the existence of lattice defects (oxygen vacancies and zinc interstitials), and (2) the particle surface sensitization by PVP.     

Magnetic and chemical properties investigation of Fe–Ni electrodeposited alloy on titanium substrate at the presence of alumina

Iron-nickel alloys have different applications in electronic systems depending on their magnetic properties. In this research, Iron-nickel alloy and its composite with Al₂O₃ particles were produced by electro wining method using a titanium cathode which is traditionally produced through a melting process (pyrometallurgy). The effect of the processing parameters on the products specification was investigated by X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and alternative gradient field magnetometer (AGFM). The produced alloy could be specified as; high saturation magnetization, low coercivity, and low magnetization, and so could be classified in the soft magnetic alloys groups. The best magnetic property of the alloy was obtained at low current density with a coercivity of about 3.10 O_e. SEM images show the cauliflower-like morphology of the product. At the presence of Al₂O₃ nanoparticles in the electrolyte, a well-dispersed particles of alumina in the alloy was observed with a decrease in the magnetization and increase in the coercivity of the alloy. Also, the modified alloy with Al₂O₃ shows better corrosion resistance in NaCl solution.

     

Effects of mechanical milling and arc-melting processes on the electrochemical performance of Si-based composite materials

The Si–Ni composite and Si/Ni alloy composite were prepared by high-energy mechanical milling and arc-melting, respectively, in order to investigate the effects of these processes on the electrochemical performance. The microstructures of Si–Ni composite and Si/Ni alloy composite were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The electrochemical properties have been investigated during 50 cycles for Si–Ni–C composite and Si/Ni alloy–C composite. As a result, both composites demonstrate a higher reversible capacity accompanied with a good cycling stability than the existing Si–C composite. Homogeneously dispersed Ni improved electric conductivity and induced fast charge transport significantly in Si–Ni–C composite whereas the secondary phases (NiSi and NiSi₂) played a role of media to accommodate a large volume change of Si during cycling in Si/Ni alloy–C composite. Consequently, it was identified that electrochemical performances of electrode material are affected by structural factors caused by the different processes.     

Hydrothermal preparation, characterization and property research of flowerlike ZnO nanocrystals built up by nanoflakes

In the present paper, flowerlike ZnO nanocrystals were successfully synthesized via a simple hydrothermal route in the presence of sodium dodecyl sulfate (SDS), employing Zn(CH₃COO)₂ and KOH as the starting reactants. The phase and morphology of the product were characterized by means of powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and select area electron diffraction (SAED). The optical properties of the product were studied. Some factors influencing the morphology of the final product including reaction time, temperature and amounts of the surfactant were discussed. Researches showed that the flowerlike ZnO nanocrystals had a good photo-catalytic activity for degradation of safranine T under 254 nm UV light irradiation. The electrochemical research of the product showed that flowerlike ZnO nanocrystals could promote electron transfers between catechol and the Au electrode. A possible formation mechanism was also suggested based on the results of the experiments.     

Fabrication of polyaniline-silver nanocomposites by chronopotentiometry in different ionic liquid microemulsion systems

Chronopotentiometry is employed to prepare polyaniline-silver (PANI-Ag) nanocomposite films in water-in-ionic liquid (W/IL) microemulsion and ionic liquid-in-water (IL/W) microemulsion. The resulted nanocomposites are characterized by scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy and X-ray diffraction. It is demonstrated that the PANI-Ag nanocomposite prepared in W/IL microemulsion is nanofibrous and the Ag nanocrystals with 5 nm diameter are dispersed homogeneously, whereas the morphology of the PANI-Ag nanocomposite prepared in IL/W microemulsion exhibits dendritic structure and the diameter of Ag nanocrystals is 50-100 nm. Further, the effects of different microemulsion systems and electrochemical synthesis conditions on the electrochemical properties of the nanocomposite films are studied by cyclic voltammetry and electrochemical impedance spectroscopy. The pure PANI films are also made for comparative purpose. It is found that the special structures of the PANI-Ag nanocomposite result in more excellent electrochemical activity than that of the pure PANI.     

Growth morphology and mechanism of primary TiC carbide in laser clad TiC/FeAl composite coating

TiC-reinforced FeAl intermetallic matrix composite (IMC) coatings were fabricated on substrate of 1Cr18Ni9Ti stainless steel using laser cladding. X-ray diffraction (XRD) was used to identify the phases in the laser clad composite coating and the growth morphologies of TiC carbide were observed by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results showed that there are two phases in the laser clad composite coating: TiC and FeAl intermetallic matrix alloy. The primary TiC carbide in laser clad coating nucleates heterogeneously on the surface of oxide particles; its growth morphology is found to be in a unique radial-branching dendrite with strongly faceted feature. The growth mechanism of TiC is confirmed to be lateral growth from the ledges or steps existing on the growing fronts.     

双向脉冲快速电沉积非晶态Ni-P/Al_2O_3复合镀层

采用双向脉冲电沉积法制备出高P非晶态Ni-P/Al_2O_3复合镀层,利用扫描电镜(SEM)和能谱分析(EDS)方法考察镀层的微观形貌和化学组成,采用X射线衍射技术(XRD)表征镀层的相结构,并通过分析金属镀层和复合镀层的电化学测试结果,评价不同种类镀层的耐腐蚀能力。结果表明:与直流电沉积法相比,双向脉冲电沉积法可将镀层中的P含量提高至12.06%(质量分数),有利于非晶态Ni-P合金镀层的形成。采用双向脉冲法制备的Ni-P/Al_2O_3复合镀层比直流电沉积法制备的Ni-P/Al_2O_3复合镀层更平整、结晶更致密。脉冲电沉积法制备的非晶态Ni-P合金镀层具有更好的耐蚀性,而且复合微粒Al_2O_3的加入,对进一步提高非晶态Ni-P合金镀层的耐蚀性有积极作用。     

尖晶石结构Ni掺杂ZnFe2O4纳米颗粒的性能表征

利用水热法成功合成了纯ZnFe2O4和不同含量Ni掺杂Zn1-xNixFe2O4纳米颗粒。采用X射线衍射(XRD)、高分辨透射电子显微镜(HRTEM)、选区电子衍射(SAED)、X射线能量色散分析(XEDS)、紫外可见吸收光谱(UV-Vis)、傅里叶变换红外光谱(FT-IR)和振动样品磁强计(VSM)等测试技术研究掺杂浓度对Zn1-xNixFe2O4(x=0,0.1,0.3,0.5)样品的晶体结构、形貌、光学性能和磁学性能的影响。结果表明:所制备的Zn1-xNixFe2O4纳米颗粒结晶良好,Ni2+以替代Zn2+的形式掺杂到ZnFe2O4晶格中,生成立方尖晶石结构ZnFe2O4。随着Ni含量的增加,晶粒尺寸增大,晶格常数发生收缩。样品的形貌呈不规则的椭球形,且颗粒大小比较均匀。红外光谱的吸收峰位置并没有随Ni掺杂浓度的增加而变化。Zn1-xNixFe2O4纳米晶的光学带隙随Ni掺杂浓度增加而增大,与相应块体相比发生蓝移。在室温下,纯ZnFe2O4纳米晶呈现超顺磁性,掺杂样品具有明显的铁磁性。