Electrodeposition and properties of Zn-nanosized TiO2 composite coatings

Nanosized TiO₂ particles were prepared by sol-gel method. The TiO₂ particles were co-deposited with zinc from a sulphate bath at pH 4.5 using electrodeposition technique. The corrosion behavior of the coatings was assessed by electrochemical polarization, impedance, weight-loss and salt spray tests. Wear resistance and microhardness of the composite coating was measured. The smaller grain size of the composite coatings was observed in the presence of TiO₂ and it was confirmed by the images of scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques.     

Preparation and characterization of nickel nano-Al2O3 composite coatings by sediment co-deposition

Ni-Al₂O₃ composite coatings were prepared by using sediment co-deposition (SCD) technique and conventional electroplating (CEP) technique from Watt's type electrolyte without any additives. The microstructure, hardness, and wear resistance of resulting composites were investigated. The results show that the incorporation of nano-Al₂O₃ particles changes the surface morphology of nickel matrix. The preferential orientation is modified from (2 0 0) plane to (1 1 1) plane. The microhardness of Ni-Al₂O₃ composite coatings in the SCD technique are higher than that of the CEP technique and pure Ni coating and increase with the increasing of the nano-Al₂O₃ particles concentration in plating solution. The wear rate of the Ni-Al₂O₃ composite coating fabricated via SCD technique with 10 g/l nano-Al₂O₃ particles in plating bath is approximately one order of magnitude lower than that of pure Ni coating. Wear resistance for SCD obtained composite coatings is superior to that obtained by the CEP technique. The wear mechanism of pure Ni and nickel nano-Al₂O₃ composite coatings are adhesive wear and abrasive wear, respectively.     

镶嵌有纳米硅的氮化硅薄膜键合特性分析

采用螺旋波等离子体化学气相沉积(HWPCVD)技术制备了非化学计量比的氢化氮化硅薄膜,对所沉积样品及氮气环境中920 ℃退火样品的微观结构及键合特性进行了分析。Raman散射结果表明,薄膜中过量硅以非晶纳米粒子形式存在,退火样品呈现纳米晶硅和氮化硅的镶嵌结构。红外吸收和可见光吸收特性比较结果显示,薄膜样品的微观结构依赖于化学计量比以及退火过程,硅含量较低样品因高的键合氢含量而表现出低的纳米硅表面缺陷态密度;退火过程将引起Si—H和N—H键合密度的减少,因晶态纳米颗粒的形成,退火样品表现出更高的结构无序度。     

Synthesis of 1,8-naphthalimide-based fluorescent nano-probes and their application in pH detection

Fluorescent nano-probes with particle sizes of 20 nm, 120 nm and 300 nm for proton were prepared through click reaction. The photophysical properties of the nano-probes were mainly affected by the particle size.     

Some insights in the sonochemical preparation of cobalt nano-particles

The preparation of cobalt nano-particles from a solution of Co(CO)₃(NO) in n-decane under ultrasonication with a frequency of 20 kHz yielded cobalt particles of a size of ca. 5 nm. The presence of either silica or oleic acid in the solution reduced the particle size to ca. 3 and 2 nm, respectively. The resulting particle size is independent of the ultrasonication time, initial Co(CO)₃(NO) concentration, ultrasound intensity and solution temperature. It is postulated that bubble collapse generates multiple nucleation sites resulting in the formation of cobalt particles with a rather uniform particle size distribution.     

Linear viscoelastic properties of electro-rheological nano-suspension confined to narrow gap between electrodes

The linear viscoelastic properties of a suspension composed of titanium dioxide nanoparticles were measured under the direct current (dc) electric field with narrow gap distances between the electrodes. The yielding behavior under no external electric fields was also discussed. The wall slip at the interface between the parallel plates and the nano-suspension was briefly discussed. Under the dc electric field, a fine chain-like microstructure was optically found within a narrow gap of 50 μm between the electrodes in the quiescent state. The nano-suspension confined to a narrow gap of 65 μm between the parallel plates was rather viscoelastic even at the highest strength of the electric field of 16 kV·mm⁻¹. Furthermore, fast and slow relaxations of the dynamic moduli were found after removal of the electric field. It was pointed out that the linear viscoelasticity was an appropriate measure of the microstructure before yielding.     

Study of water properties in nanospace

Here we report an anomalous behavior of water, especially its viscosity and hydrodynamic flow, in a nanometer-confined space. As a typical model of a nanometer-confined space, the nanopillar chip, which was developed for DNA size-based separation was used, and single-particle tracking (SPT) technique was applied to investigate water viscosity and hydrodynamic flow in the nanopillar chip. The diffusion coefficients of nanospheres were almost one-third of the theoretical value derived from the Stokes-Einstein equation. This result gave indirect proof that water viscosity in a nanometer-confined space is higher than in a bulk solution. In order to improve resolution and throughput of the nanopillar chip for DNA separation, these potential factors affecting performance should be seriously considered.     

Tuning of particle plasmon resonances in binary dielectric medium

Using light scattering spectroscopy, I demonstrate an approach to tune particle plasmon resonance in a binary dielectric media where silver nano-rods are embedded partially both in Anodic Aluminum Oxide (AAO) matrix and in air. A systematic experimental study under a controlled variation of the degree of embedding of nano-rods in AAO matrix has been presented. Experimental results have been interpreted based on the Drude model. Finite Difference Time Domain (FDTD) method has been employed to calculate the nature of the silver nano-rod resonance at the experimental conditions. Both the simulation results and theory corroborate the experimental findings.     

含树枝状大分子PAMAM的苯乙烯乳液聚合

将树枝状大分子PAMAM (4 5代 )作为种子 ,以苯乙烯为代表性单体进行乳液聚合 .研究结果表明 ,加入树枝状大分子PAMAM时 ,所制得的聚合物乳液粒子平均粒径在 30～ 5 0nm之间 ,小于 10 0nm ,且大小分布均匀 ;所制备的聚合物在 16 70cm- 1 左右处出现酰胺的特征吸收峰 ,在 330 0cm- 1 左右处出现N—H伸缩振动特征峰 ;说明树枝状大分子PAMAM起到种子的作用 ,所制备的聚合物含树枝状大分子PAMAM .     

纳米颗粒光子相关测定中基线方法对测量结果的影响

从光场自相关函数(Autocorrelation Function,ACF)与光强ACF、衰减率分布函数的关系,推导了基线值对有效直径、分散度的影响.分析了决定基线值取值的两种基线方法,指出基线方法不同,基线值也会不同.对三种纳米颗粒样品的相关实验也证明基线值越大,颗粒的有效直径、分散度越小.分析了自动斜率法的测量结果较稳定的原因.