碳酸钙的偶联剂改性及对SBS力学性能的影响

为进一步改善超细CaCO3的表面活性,利用γ-氨基丙基三乙氧基硅烷偶联剂(KH-550)对超细CaCO3进行表面改性,采用密炼工艺制备了超细CaCO3/热塑性丁苯橡胶(SBS)复合材料.通过红外光谱(FT-IR)、热重分析(TGA)、接触角测定仪(CAMI)和粒径分析等研究了改性前后超细CaCO3的结构变化,采用橡胶加工分析仪(RPA)和扫描电子显微镜(SEM)等对改性前后超细CaCO3的复合材料的力学性能和微观形貌进行了测试分析.结果表明:硅烷偶联剂KH-550与超细CaCO3粉体间能形成化学结合,修饰后的超细Ca-CO3能有效阻止颗粒间团聚,并均匀分散在橡胶胶体中,与胶体间形成物理和化学交联结构;改性后超细Ca-CO3在SBS体系中能形成网状结构,材料力学性能明显提高;当活化超细CaCO3的质量分数为20%时,能获得性能优异的复合材料.     

Preparation and electrochemical performance of LiFePO4/C composite with network connections of nano-carbon wires

LiFePO₄/C composite with network connections of nano-carbon wires was successfully prepared by using polyvinyl alcohol as carbon source. The composite was characterized by X-ray diffraction and transmission electron microscopic, and its electrochemical performance was investigated by galvanostatic charge and discharge tests. The experimental results show that LiFePO₄ grains are tightly connected by the network of nano-carbon wires. Moreover LiFePO₄/C composite exhibits high capacity of 168 mAh g⁻¹ applied 15 mA g⁻¹ current density (C/10), excellent cyclic ability and rate capability. When 1500 mA g⁻¹ current density (10C) was applied, the high discharge capacity of 129 mAh g⁻¹ has been obtained at room temperature.     

A novel anode material of Fe2VO4 for high power Lithium ion battery

Spinel Fe₂VO₄ was synthesized by solid state method and its properties were characterized using XRD, SEM, TG-DSC and specific surface area measurements. The average size of the particles was 500 nm. TG-DSC test demonstrated that the Fe₂VO₄ was thermally stable in nitrogen atmosphere within 300 °C. Lithium insertion into the sample at room temperature and 55 °C has been investigated and the highest discharge capacity approached 250 mAh/g at an average voltage of 0.6 V vs Li⁺/Li. Capacity retention was unexpectedly good at 1C discharge rate at room temperature and 55 °C. At 5C discharge rate, the specific capacity was still 136 mAh/g. The results show that the Fe₂VO₄ is a promising anode material due to its high specific capacity, thermal stability and rate performances.     

Structure and magnetic properties of FeCo-SiO2 nanocomposite synthesized by a novel wet chemical method

A novel soft magnetic nanocomposite with FeCo particles encapsulated by amorphous SiO₂ was synthesized using a co-precipitation combined H₂ reduction method. The saturation magnetization of the (Fe₇₀Co₃₀)₉₀/(SiO₂)₁₀ nanocomposite is as high as 200 emu/g, which is 4-5 times larger than that of traditional spinel ferrites. The frequency dependence of the complex initial permeability is intensely dependent upon the content of SiO₂ insulating phase. With increasing the content of SiO₂ to 10 wt.%, the cut-off frequency is drastically increased to over 1 GHz. The results show that a new high-frequency soft magnetic material with high saturation magnetization (M_s) can be achieved by introducing FeCo/SiO₂ nanocomposite.     

Preparation of Fe3O4/PVA nanofibers via combining in-situ composite with electrospinning

A novel approach, combining in-situ composite method with electrospinning, was used to prepare high magnetic Fe₃O₄/poly(vinyl alcohol) (PVA) composite nanofibers. Fe₃O₄ magnetic fluids were synthesized by chemical co-precipitation method in the presence of 6 wt.% PVA aqueous solution. PVA was used as stabilizer and polymeric matrix. The resulting Fe₃O₄/PVA composite nanofibers were characterized with field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray diffractometer (XRD), respectively. These composite fibers showed a uniform and continuous morphology, with the Fe₃O₄ nanoparticles embedded in the fibers. Magnetization test confirmed that the composite fiber showed a high saturated magnetization (M_s = 2.42 emµ·g^-1) although only 4 wt.% content.     

Synthesis and characterization of Co3O4/RuO2 composite nanofibers fabricated by an electrospinning method

Co₃O₄-RuO₂ composite nanofibers (NFs) were synthesized by an electrospinning method and were calcinated at 400°C for 1 hr in air. Scanning electron microscopy and high-resolution transmission electron microscopy (HRTEM) examinations show that all the synthesized NFs have uniform surface morphology and their diameters are in the range of ~ 30-~70 nm. X-ray diffraction (XRD) results show that crystalline Co₃O₄ phase and RuO₂ phase coexist in the composite NF matrix which is confirmed by X-ray photoemission spectroscopy. In addition, the HRTEM energy-dispersive X-ray spectroscopy mapping results show that the Co₃O₄ and RuO₂ phases are uniformly distributed across the NF matrix.     

Preparation and characterization of magnetic nanofibrous composite membranes with catalytic activity

Magnetic nanofibrous composite membranes were electrospun from the mixtures of poly(acrylonitrile-co-acrylic acid) (PANCAA) and Fe₃O₄ nanoparticles. Field emission scanning electron microscopy (FESEM) and thermal gravimetric analysis (TGA) were used to characterize the composite membranes. TGA results indicate that the addition of Fe₃O₄ nanoparticles catalyzes the carbonization of PANCAA as well as dramatically increases the carbonization temperature. The intrinsic peroxidase-like activity of Fe₃O₄ nanoparticles was measured by the color reaction of phenol/4-amino antipyrine in the presence of H₂O₂. Under optimal conditions, the electrospun composite membranes show high peroxidase-like catalytic activity and reusability. Taking into account of the potentiality for separation, these as-prepared magnetic nanofibrous composite membranes will be applied in phenolic wastewater treatment.     

DNA-like dye-sensitized solar cells based on TiO2 nanowire-covered nanotube bilayer film electrodes

This paper reports a two-step formation of a TiO₂ nanowire-covered nanotube bilayer film technique and its application in DNA-like dye-sensitized solar cells. The bilayer film was prepared by the electrochemical anodization first and then the hydrothermal method. From the reflectivity spectrum and scanning electron microscopy it is observed that the nanowire layer on the top cannot only decrease the reflectivity of the film, but also play a role to modify the film cracks. Compared with the dye-sensitized solar cells based on a single layer electrode, the cell with the bilayer film showed higher photovoltaic parameters and a lower dark current, which is due to its higher light harvesting efficiency and lower charge recombination between the electrolyte and the substrates.     

Preparation of Ni nanoparticle-TiO2 nanotube composite by pulse electrodeposition

A Ni/TiO₂ nanocomposite was successfully prepared by a pulse electrodeposition (PED) technique. Highly-ordered TiO₂ nanotube arrays fabricated by anodization were employed as a substrate and loaded with Ni nanoparticles by PED. The influence of pulse electrodeposition parameters was investigated on the morphology of nickel electrodeposits. The nanocomposite was characterized by field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The results indicated that Ni nanoparticles with average size ranging from 19 to 84 nm were obtained by changing electrodeposition parameters. At constant current off-time (t_off) and pulse time of both negative and positive currents, the particle size decreased asymptotically with increasing amplitude of both negative and positive current. A progressive decrease of the particle size was observed with increasing current off-time at constant amplitude and pulse time of both negative and positive current. Increase in the deposition time at constant current off-time, amplitude and pulse time of both negative and positive current resulted in particle growth.     

Improvement of magnetic characteristics and electrical properties of FeCoHfO/AlOx multilayered films

High permeability magnetic films can enhance the inductance of thin-film inductors in DC-DC converters. In order to obtain high permeability, effective uniaxial anisotropic field should be as low as possible. A multilayered technique (laminating the magnetic layers with oxide spacers) was exploited to improve the magnetic properties of thick films. The FeCoHfO/AlO_x multilayered films were fabricated by dc reactive magnetron sputtering. Inserting an insulator (AlO_x) layer can decrease the magneto-elastic anisotropy by reducing the residual stress of the FeCoHfO magnetic films. The anisotropic field and resistivity of the FeCoHfO/AlO_x multilayered films were evidently improved by multilayered coating. With this optimum configuration of 9 layers structure [FeCoHfO (133 nm)/AlO_x (10 nm)]₉, low anisotropic field (H_K = 65 Oe) and high resistivity (ρ ∼ 1350) μΩ cm were achieved.     

Effect of working pressure on the properties of BaTiO3-CoFe2O4 composite films deposited on STO (100) by PLD

The BaTiO₃-CoFe₂O₄ (BTO-CFO) composite films were grown on SrTiO₃ (STO) (100) substrates at 750 °C under various working pressures by pulsed laser deposition. The composite film grew into a supersaturated single phase at the working pressure of 10 mTorr, BTO and CFO (00 l) oriented hetero-epitaxial films on STO (100) at 100 mTorr, and a polycrystalline composite film at 500 mTorr. The slow growth rate at high working pressure led to the phase separation in the composite film. The CFO was compressively strained along out-of-plane due to the lattice mismatch with the BTO matrix phase. The BTO-CFO composite film grown at 100 mTorr showed reversible switching of ferroelectric polarization and magnetic hysteresis with strong magnetic anisotropy.     

A novel lanthanum hydroxide nanostructure prepared by cathodic electrodeposition

A novel and interesting nanostructure of La(OH)₃ was prepared by electrochemical method under mild conditions without any hard templates and surfactants. In this method, La(OH)₃ was galvanostatically deposited from low-temperature nitrate bath on the steel substrate by electrogeneration of base. X-ray results showed that the obtained deposit has single crystalline hexagonal phase of La(OH)₃. Morphological characterization revealed that the product has compact morphology with capsule-like structures having approximately an average diameter of 15 nm and the length of up to 50 nm. The results showed that low-temperature cathodic electrodeposition can be recognized as an easy and facile method for the synthesis of La(OH)₃ nanocapsules.     

Preparation and characterization of SnO2/carbon nanotube composite for lithium ion battery applications

SnO₂/multi-walled carbon nanotube (MWCNT) composite was prepared via a diffusion method. Firstly the MWCNT was sonicated in a filtrate which was derived from a tin dichloride solution mixed with AgNO₃ solution. Then the SnO₂/MWCNT composite was prepared whereby, after calcination in N₂ atmosphere, the salts inside the MWCNT decomposed to SnO₂. The resulting composite was characterized by transmission electron microscopy, Raman spectroscopy and X-ray diffraction, which indicated that SnO₂ had infiltrated into the MWCNT and filled the interior. The subsequent evaluation of the electrochemical performance in lithium ion batteries showed that the SnO₂/MWCNT composite had a reversible discharge capacity of 505.9 mAh?g^− 1 after 40 cycles, as compared to 126.4 mAh?g^− 1 for pure nano-SnO₂.     

A true nanocomposite: Single crystalline Au nanoparticles on single crystalline Fe3O4 nanoparticles

An Au/Fe₃O₄ nanocomposite catalyst was fabricated through a simple deposition-precipitation method. The Au/Fe₃O₄ nanocomposite is a true nanocomposite that has single crystalline Au nanoparticles supported on single crystalline Fe₃O₄ nanoparticles. Lattice fringes from both Au and Fe₃O₄ single nanoparticles were simultaneously observed by transmission electron microscope (TEM). This nanocomposite catalyst showed much high activity in low temperature CO oxidation reaction. The Au/Fe₃O₄ nanocomposite catalyst reaches 100% CO conversion at 40 °C. In comparison, Au/commercial Fe₃O₄ catalyst needs 375 °C to convert CO. This Au/Fe₃O₄ nanocomposite is an ideal sample to study synergetic effect between the catalyst and the support at nanoscale.     

Thermal stability of nano-layered structure and hardness of TiAlN/Si3N4 nanoscale multilayered coating

Thermal stability of the TiAlN/Si₃N₄ nanoscale multilayered coating that was reported to show excellent hardness and toughness, has been investigated in terms of the nano-layered structure and hardness. TiAlN/Si₃N₄ nanoscale multilayered coatings with various thickness of Si₃N₄ layer were prepared by alternating deposition of TiAlN and Si₃N₄. In contrast to other nanoscale multilayered coating system such as AlN/CrN in which the intensity of the low angle XRD peaks decreases with increasing annealing temperature by interdiffusion between adjacent layers, the low angle XRD peak intensity of the nanoscale multilayered TiAlN/Si₃N₄ coatings increased after heat-treatment in an N₂ atmosphere up to 800 °C. Such a thermal stability of the nano-layered structure is believed to be due to spinodal type phase separation of TiAlN and Si₃N₄, which increased the hardness value of the TiAlN/Si₃N₄ coating at high temperatures.     

Preparation and electrochemical performance of LiFePO4/C composite with carbon core structure

LiFePO₄/C composite with carbon core structure was successfully prepared by using araldite as carbon source. The microstructure and morphology of LiFePO₄/C composite were confirmed by X-ray diffraction and transmission electron microscopic observation. The experimental results show that this structure is entirely different from carbon coating. The LiFePO₄/C composite forms a common core structure in which carbon is used as line core and carbon core is covered by nano-LiFePO₄ grains. Moreover, the LiFePO₄/C composite exhibits higher tap density of 1.66 g cm^− 3, shows higher capacity about 162 mAhg^− 1 applied 30 mAg^− 1 current, excellent cyclic ability and rate capability about 139 mAhg^− 1 applied 700 mAg^− 1 current at room temperature.     

ZnO复合石墨相氮化碳纳米片的制备及其光催化性能研究

为了提高石墨相氮化碳光催化性能,本文以尿素、硫脲、醋酸锌为前驱体,通过氧化热剥离与共混煅烧法分别制备g-C₃N₄纳米片和ZnO/g-C₃N₄异质结复合材料,并采用TEM、FTIR、XRD、UV-Vis DRS、BET等表征手段对制备的催化剂进行结构表征。以罗丹明、大肠杆菌为探针,考察了催化剂的光催化降解性能和抑菌活性。结果表明：以尿素和硫脲为前驱体,经过氧化热剥离处理后能得到的g-C₃N₄ 2D纳米片,其比表面积更大、光催化性能更加优异,且其对罗丹明的降解率较未剥离的g-C₃N₄提高了21.2%。在40 min氙灯照射下,纯g-C₃N₄并未表现出良好的抑菌性能,而通过ZnO复合制备的ZnO/g-C₃N₄异质结复合材料,在光催化降解率和抑菌活性方面均有很大提高,其中复合20%ZnO制得的ZnO异质结复合材料表现出最佳的光催化性能...     

Micro-sized and Nano-sized Fe_3O_4 Particles as Anode Materials for Lithium-ion Batteries

Micro-sized(1030.3±178.4 nm) and nano-sized(50.4±8.0 nm) Fe3O4 particles have been fabricated through hydrogen thermal reduction of α-Fe2O3 particles synthesized by means of a hydrothermal process.The morphology and microstructure of the micro-sized and the nano-sized Fe3O4 particles were characterized by X-ray diffraction,field-emission gun scanning electron microscopy,transmission electron microscopy and highresolution electron microscopy.The micro-sized Fe3O4 particles exhibit porous structure,while the nano-sized Fe3O4 particles are solid structure.Their electrochemical performance was also evaluated.The nano-sized solid Fe3O4 particles exhibit gradual capacity fading with initial discharge capacity of 1083.1 mAhg-1 and reversible capacity retention of 32.6% over 50 cycles.Interestingly,the micro-sized porous Fe3O4 particles display very stable capacity-cycling behavior,with initial discharge capacity of 887.5 mAhg-1 and charge capacity of 684.4 mAhg-1 at the 50th cycle.Therefore,77.1% of the reversible capacity can be maintained over 50 cycles.The micro-sized porous Fe3O4 particles with facile synthesis,good cycling performance and high capacity retention are promising candidate as anode materials for high energy-density lithium-ion batteries.     

Selection of scattering enhancement particles for improving color homogeneity and luminous flux of phosphor-converted LEDs

Abstract

At the present time, color homogeneity and luminous flux are the two essentials utilized to appraise high-quality phosphor-converted LEDs (pcLEDs). In this paper, we present the search for the optimal selection among scattering enhancement particles (SEPs) to apply to improve these essentials for pcLEDs having correlated color temperature of 8500 K. The interested contenders include CaCO₃, CaF₂, SiO₂, and TiO₂. Each of them is added to yellow phosphor compounding (Y₃Al₅O₁₂:Ce³⁺). Firstly, the LightTools program is employed to do the optical simulations. Secondly, the obtained results are verified and analyzed based on Mie scattering theory. The scattering computation of SEPs includes the scattering coefficients, the anisotropic scattering, the reduced scattering and the scattering amplitudes at 455 and 595 nm. It is observed that TiO₂ particles provide the highest color homogeneity among the SEPs but the luminous flux reduces significantly as its concentration increases. By using CaCO₃ particles, the highest luminous flux of 792 lm is obtained. CaCO₃ particles can also reduce the deviation of color correlated temperature to 620 K at 30% concentration. Therefore, CaCO₃ particles should be selected to enhance both color homogeneity and luminous flux.     

Low temperature facile synthesis of anatase TiO2 coated multiwalled carbon nanotube nanocomposites

Anatase TiO₂ coated multiwalled carbon nanotube (MWNT) nanocomposites were prepared by combining the sol-gel method with a self assembly technique at a low temperature. XRD, TEM, FTIR and XPS spectra were applied to characterize the crystal phase, microstructure, and other physicochemical properties of the sample. The results showed that MWNTs were covered with a 12-20 nm thickness layer of anatase TiO₂ or surrounded by a 30 -290 nm thickness coating of anatase TiO₂. The layer or coating is constructed of TiO₂ nanoparticles about 5.8 nm. Furthermore, as-prepared composite was rich in surface hydroxyl groups.