w-BN(001)B面上铁(钴、镍)纳米线的高自旋极化研究

文章用密度泛涵理论(DFT)和广义梯度近似(GGA)研究了铁、钴和镍在纤锌矿结构氮化硼(w-BN)(001)B面上排列的纳米线的电子结构和磁性,计算了原子的磁矩和态密度,发现在w-BN(001)的B面上的铁和钴纳米线具有高自旋极化的特性,并与孤立的铁、钴和镍原子线的电子结构进行了比较研究,这种高自旋极化材料在微电子器件中可以用作自旋过滤器.

Molecular dynamics study on temperature and strain rate dependences of mechanical tensile properties of ultrathin nickel nanowires

Based on the EAM potential, a molecular dynamics study on the tensile properties of ultrathin nickel nanowires in the （100〉 orientation with diameters of 3.94, 4.95 and 5.99 nm was presented at different temperatures and strain rates. The temperature and strain rate dependences of tensile properties were investigated. The simulation results show that the elastic modulus and the yield strength are gradually decreasing with the increase of temperature, while with the increase of the strain rate, the stress--strain curves fluctuate more intensely and the ultrathin nickel nanowires rupture at one smaller and smaller strain. At an ideal temperature of 0.01 K, the yield strength of the nanowires drops rapidly with the increase of strain rate, and at other temperatures the strain rate has a little influence on the elastic modulus and the yield strength. Finally, the effects of size on the tensile properties of ultrathin nickel nanowires were briefly discussed.

Study on the Influence of Ni Modifying on Phase Transformation and Photocatalytic Activity of TiO_2

The Ni-modified TiO2 was synthesized using two methods including co-precipitation(Ni doped TiO2, Ni-TiO2) and wet impregnation(Ni loaded TiO2, Ni/TiO2). The surface and bulk crystalline phases of Ni-modified TiO2 were investigated by using X-ray diffractometry(XRD), UV Raman spectroscopy, TEM, and SEM. It is observed that Ni doping can promote the phase transition and grain size growth of TiO2. Moreover, the propagation of the rutile phase from the bulk into the surface region of TiO2 is increased when the Ni doping amount reaches up to 3%. However, in Ni/TiO2, it is found out that the surface and bulk phase transformation of TiO2 can be inhibited after impregnation of 1% of Ni on the TiO2. Compared with the co-precipitation method, Ni species may be more enriched in the surface of the Ni/TiO2 sample upon adoption of the impregnation method, and the direct contact of anatase particles of TiO2 is avoided. As a consequence, the phase transition in the surface and bulk region of TiO2 can be effectively inhibited by Ni loading. Additionally, the activity of the photocatalytic degradation of RhB on the 3Ni-TiO2-600 ℃ sample is higher than that on the 3 Ni/TiO2-600 ℃ sample. The phase junction formed between anatase and rutile in the surface region of 3Ni-TiO2-600 ℃ may the main reason for its high photocatalytic activity.

Ab Initio Study on Structural and Magnetic Properties of Ni-Pd and Ni-Pt Linear and Zigzag Nanowires

Employing the accurate frozen-core full-potential projector augmented-wave method,the self-consistentelectronic structure calculations were carried out on pure Ni,Pd,Pt and mixed Ni-Pd and Ni-Pt free-standing linear andzigzag nanowires.The bond lengths for all these systems are generally increased as their structures change from the linearto the zigzag chain.The bond lengths for Ni-Pd and Ni-Pt wires are in between the values of corresponding pure systemand the bond angles around 60° suggesting the possible formation of Ni-Pd and Ni-Pt bimetallic materials.In mixedNi-Pd and Ni-Pt chains,the Ni,Pd,and Pt atoms have quite high local magnetic moments.The calculations suggestthat the magnetic moments in linear nanowires are generally larger than the ones of corresponding zigzag nanowires.Itis found that there is hybridization between Ni 3d and Pd 4d,Ni 3d and Pt 5d states,which may significantly affectstructural stability and magnetism of Ni-Pd and Ni-Pt nanowires.

Electrodeposition of Ni-Co-Fe_2O_3 composite coatings

Ni-Co-Fe2O3 composite coatings were electrodeposited using cetyltrimethylammonium bromide(CTAB)-modified Watt's nickel bath with Fe2O3 particles dispersed in it.The effects of the plating parameters on the chemical composition,structural and morphological characteristics of the electrodeposited Ni-Co-Fe2O3 composite coatings were investigated by energy dispersive X-ray(EDS) spectroscopy,X-ray diffractometry(XRD) and scanning electron microscopy(SEM).The results reveal that Fe2O3 particles can be codeposited in the Ni-Co matrix.The codeposition of Fe2O3 particles with Ni-Co is favoured at high Fe2O3 particle concentration and medium stirring,and the deposition of Co is favoured at high concentration of CTAB.Moreover,the study of the textural perfection of the deposits reveals that the presence of particles leads to the worsening of the quality of the observed <220> preferred orientation.Composites with high concentration of embedded particles exhibit a preferred crystal orientation of <111>.The more the embedded Fe2O3 particles in the metallic matrix,the smaller the sizes of the crystallite for the composite deposits.

Growth and magnetic properties of single crystalline Ni nanowire arrays prepared by pulse DC electrodeposition

Highly textured Ni nanowire arrays were fabricated into anodic aluminum oxide （AAO） templates by pulse DC electrodeposi- tion. The applied voltage and pH value of electrolytes were found strongly affecting the microstrucmre and magnetic proper ties of Ni nanowire arrays. Low applied potential and pH value both prefer to form polycrystalline fcc Ni nanowires. Increas- ing the applied potential or pH value favors the Ni [220] texture and even eventually forms the [220] oriented single crystal Ni wires, while exorbitant potential and pH value will conversely weaken the texture of nanowires. The magnetic properties of Ni wires are closely related to the microstructure of Ni nanowire arrays and large coercivities more than 1000 Oe were achieved at single crystalline Ni nanowire arrays. The mechanisms for the effect of applied potential and pH value on the grain size, tex- ture and magnetic properties of Ni nanowire arrays have been discussed.

Atomic-scale Pt clusters decorated on porousα-Ni(OH)_2 nanowires as highly efficient electrocatalyst for hydrogen evolution reaction

The synthesis of atomic-scale metal catalysts is a promising but very challenging project. In this work, we successfully fabricated a hybrid catalyst of PL/Ni（OH）2 with atomic-scale Pt clusters uniformly decorated on porous Ni（OH）2 nanowires （NWs） via a facile room-temperature synthesis strategy. The as-obtained Ptc/Ni（OH）2 catalyst exhibits highly efficient hydrogen evolution reaction （HER） performance under basic conditions. In 0.1moll-1 KOH, the Ptc/Ni（OH）2 has an onset overpotential of -0 mV vs. RHE, and a significantly low overpotential of 32 mV at a current density of 10mAcm-2, lower than that of the com- mercial 20% Pt/C （58 mV）. The mass current density data illustrated that the PL/Ni（OH）2 reached a high current den- sity of 6.34Amg^-1i at an overpotential of 50 mV, which was approximately 28 times higher than that of the commercial Pt/C （0.223Amg^-1i） at the same overpotential, proving the high-efficiency electrocatalytic activity of the as-obtained Ptc/Ni（OH）2 for HER under alkaline conditions.

Fabrication and properties of well-ordered arrays of single-crystalline NiSi2 nanowires and epitaxial NiSi2/Si heterostructures

In this study, we reported the design, fabrication, and characterization of well- ordered arrays of vertically-aligned, epitaxial NiSi2/Si heterostructures and single- crystalline NiSi2 nanowires on （001）Si substrates. The epitaxial NiSi2 with {111} facets was found to be the first and the only silicide phase formed inside the Si nanowires after annealing at a temperature as low as 300℃. Upon annealing at 500 ℃ for 4 h, the residual parts of Si nanowires were completely consumed and the NiSi2/Si heterostructured nanowires were transformed to fully silicided NiSi2 nanowires. XRD, TEM and SAED analyses indicated that all the NiSi2 nanowires were single crystalline and their axial orientations were parallel to the [001] direction. The obtained vertically-aligned NiSi2 nanowires, owing to their well-ordered arrangement, single-crystalline structure, and low effective work function, exhibit excellent field-emission properties with a very low turn-on field of 1.1 V/m. The surface wettability of the nanowires was found to switch from hydrophobic to hydrophilic after the formation of NiSi2 phase and the measured water contact angle decreased with increasing extent of Ni silicidation. The increased hydrophilicity can be explained by the Wenzel model. The obtained results present the exciting prospect that the new approach proposed here will provide the capability to fabricate other highly-ordered, vertically-aligned fully silicided nanowire arrays and may offer potential applications in constructing vertical silicide-based nanodevices.

In-situ characterization of metal nanoparticles and their organic coatings using laser-vaporization aerosol mass spectrometry

The development of methods to produce nanoparticles with unique properties via the aerosol route is progressing rapidly. Typical characterization techniques extract particles from the synthesis process for subsequent offiine analysis, which may alter the particle characteristics. In this work, we use laser-vaporization aerosol mass spectrometry （LV-AMS） with 70-eV electron ionization for real-time, in-situ nanoparticle characterization. The particle characteristics are examined for various aerosol synthesis methods, degrees of sintering, and for controlled condensation of organic material to simulate surface coating/functionalization. The LV-AMS is used to characterize several types of metal nanoparticles （Ag, Au, Pd, PdAg, Fe, Ni, and Cu）. The degree of oxidation of the Fe and Ni nanoparticles is found to increase with increased sintering temperature, while the surface organic-impurity content of the metal particles decreases with increased sintering temperature. For aggregate metal particles, the organic-impurity content is found to be similar to that of a monolayer. By comparing different equivalent-diameter measurements, we demonstrate that the LV-AMS can be used in tandem with a differential mobility analyzer to determine the compactness of synthesized metal particles, both during sintering and during material addition for surface functionalization. Further, materials supplied to the particle production line downstream of the particle generators are found to reach the generators as contaminants. The capacity for such in-situ observations is important, as it facilitates rapid response to undesired behavior within the particle production process. This study demonstrates the utility of real-time, in-situ aerosol mass spectrometric measurements to characterize metal nanoparticles obtained directly from the synthesis process line, including their chemical composition, shape, and contamination, providing the potential for effective optimization of process operating parameters.