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.     

Biodegradable polyester hybrid nanocomposites containing titanium dioxide network and poly(ε-caprolactone): Synthesis and characterization

In this paper, biodegradable poly(ε-caprolactone)/titanium dioxide hybrid film materials were prepared via in situ sol-gel process with tetrabutyl titanate (TBT) as inorganic precursor in the presence of poly(ε-caprolactone) and were characterized by means of Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electronic microscopy (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The hybrids displayed microphase-separated structure on the nanometer scale. The studies of crystallization and melting behaviors of the hybrid films indicate that TiO₂ inorganic components have a considerable influence on behavior of crystallization of poly(ε-caprolactone) in hybrid materials.     

Synthesis and characterisation of nanostructured silica-powellite-HAP composites

Well-defined calcium molybdate (CaMoO₄) and hydroxyapatite (HAP) nanocrystals were developed by thermal treatment on the surface of a SiO₂–CaO–P₂O₅–MoO₃ amorphous precursor synthesised at room-temperature by sol–gel route. The structural and morphological characterisaions were performed by several techniques: energy dispersive X-ray spectroscopy, thermal analyses (DTA/TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy, electron paramagnetic resonance. Complementary, Fourier transform infrared and Raman spectroscopies provided a clear picture regarding the short range order structure, emphasising beside the CaMoO₄ phase development, the presence of HAP nanocrystals. The vibrational spectroscopic techniques proved to be valuable tools for evidencing very small HAP nanocrystallites that cannot be clearly observed by XRD and TEM analyses.     

Light emission from high-k dielectrics containing Ge nanocrystals

A Ge light-emitting diode (LED) is demonstrated using a metal-insulator-semiconductor (MIS) tunneling structure with Ge nanocrystals (NCs) embedded within the insulator. A high-k dielectric insulator was used and the Ge NCs were grown by co-sputtering onto p-type Si substrates. Electron-hole radiative recombination within the Ge NCs (grown within HfAlO) allowed for the observation of infrared emission. Visible light was also detected due to defect-related radiative recombination at the Ge/HfAlO interface. The NC size and Ge content were measured using transmission electron microscopy (TEM), energy dispersive X-ray (EDX) spectroscopy and Raman spectroscopy. The peak wavelength from the photoluminescence experiments was lower when HfAlO was used as the dielectric than when HfO₂ was used. This is likely due to the larger band gap of HfAlO, when compared to HfO₂.     

Large-scale synthesis of nanocrystals of barium titanate and other titanates through solution-phase processes

We reported a large-scale synthesis of nanocrystals of BaTiO₃, SrTiO₃, PbTiO₃, Sr_xBa_1−xTiO₃ through low-temperature and solution-phase processes without any surfactant. The series of samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Samples obtained were of high purity, consisting of nanoparticles with fine crystallinity and uniformity as well as good dispersibility in ethanol. This method might also offer an effectively new way to synthesis other titanate nanocrystals with perovskite structure in the future.     

Synthesis and characterization of Mn2O3 nanorods using a novel manganese precursor

The Mn₂O₃ nanorods have been prepared using [Mn(sal)₂] complex as a novel precursor in the presence of sodium dodecyl sulfate (SDS) as surfactant. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) spectroscopy. Manganese oxide nanocrystals have been prepared under different condition. The controlled experimental results showed that the ultrasonic irradiation and the use of SDS as the surfactant in the chemical process play important role in the formation of the final products.     

Preparation and characterization of perovskite LaFeO3 nanocrystals

Orthorhombic structure perovskite LaFeO₃ nanocrystals with size of 59 nm were prepared by glycine combustion method. The as-prepared LaFeO₃ nanocrystals were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high reaction transmission electron microscopy (HRTEM), energy dispersive X-ray spectrometer (EDS), scanning electron microscope (SEM), UV–Visible absorption spectroscopy, Laser Raman Spectroscopy (LRS) and Brunauer–Emmett–Teller (BET) nitrogen adsorption. The preparation process can be also applied to synthesize other complex oxides such as NdFeO₃, LaCoO₃ and LaNiO₃.     

Bi2O3纳米晶玻璃三阶非线性光吸收性质的研究

利用溶胶凝胶法结合气氛控制方式合成了含Bi2O3纳米晶钠硼硅玻璃.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)、高分辨透射电子显微镜(HRTEM)以及选区电子衍射(SAED)对掺杂在钠硼硅玻璃中Bi2O3纳米晶的形貌和微结构进行了表征,同时,利用飞秒开孔Z-scan技术详细地研究了Bi2O3纳米晶玻璃在800 nm处不同激发光强度下的三阶非线性光吸收性质.结果表明,在钠硼硅玻璃中形成了尺寸小于10 nm的Bi2O3单斜晶系纳米晶.随着激发光强度的增强,该玻璃的三阶非线性光吸收性质产生由饱和吸收向反饱和吸收的转变.进一步,计算得到的该玻璃三阶非线性极化率χ(3)的数量级范围在10-19~10-18m2/V2之间.这一结果说明该玻璃具有良好的非线性光学性能,并且在光限幅器等非线性光学领域具有潜在的应用价值.     

Preparation of PbS-type PbO nanocrystals in a room-temperature ionic liquid

In a strong polar environment of ionic liquid 1-n-butyl-3-ethylimidazolium tetrafluoroborate [BEIM]BF₄, PbO nanocrystals with PbS-type crystal structure were successfully synthesized by the thermal decomposition of Pb(OH)₂ at 180 °C for 3 h under ambient pressure. The product was characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), electric diffraction (ED), X-ray photoelectron spectrum (XPS) and elemental analysis.     

Controlled synthesis of calcium carbonate nanocrystals with multi-morphologies in different bicontinuous microemulsions

The nucleation and growth of calcium carbonate nanocrystals were studied in two types of bicontinuous microemulsions, consisted of P-octyl polyethylene glycol phenylether (OP)/n-amyl alcohol/cyclohexane/water, and the above microemulsion containing dl-aspartic acid (dl-Asp). The produced CaCO₃ nanocrystals were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectrometer (FT-IR) and X-ray diffraction (XRD). The results indicated that OP and dl-Asp used as soft template could control synthesis of CaCO₃ nanocrystals well. The various shapes of CaCO₃ nanocrystals, such as solid sphere, network, whisker, rod, and hollow sphere were successfully prepared by altering the concentration of the reactants, adding dl-Asp, and adjusting the pH values of dl-Asp/CaCl₂ aqueous solution. Sole calcite phase was obtained in OP bicontinuous microemulsion. The presence of dl-Asp was helpful for the formation of thermodynamically unstable vaterite phase. In OP/dl-Asp bicontinuous microemulsion, the higher pH value of dl-Asp/CaCl₂ aqueous solution is, the more vaterite will be formed. A nucleation-limited growth and limited aggregation (NGA) model was used to explain growth mechanism of the network-like calcium carbonate in this study.     

Integration of stacked capacitor module with ultra-thin ferroelectric SrBi2Ta2O9 film for high density ferroelectric random access memory applications at low voltage operation

The crystallization route of thin SrBi₂Ta₂O₉ (SBT) films deposited on Pt(100 nm)/Ti(10 nm)/SiO₂/Si substrate is investigated at different annealing temperatures by atomic force microscopy (AFM) and X-ray diffractometry (XRD). To evaluate the SBT film properties for low voltage operation and for high storage density (>16 MBit), SBT is deposited at different film thicknesses. Furthermore, the performance of a Pt/SBT/Pt capacitor on a barrier-/contact-layer/polysilicon-plug architecture suitable for stacked capacitor memories is investigated by transmission electron microscopy (TEM)/energy dispersive X-ray analysis (EDX) and electrical measurements. It is shown that an oxidized and highly resistive contact layer can be recovered by electrical pulses. Finally, a process solution for a successful integration of 38 nm thin SBT films into this structure is provided.     

Synthesis of nanocrystalline GaN by the sol–gel method

Single-phase wurtzite GaN nanocrystals with an average diameter of 11 ± 3 nm were synthesized by the sol–gel technique from readily available Ga(NO₃)₃. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) confirmed they had a hexagonal structure and a narrow size distribution of the nanocrystals. X-ray powder diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) measurement showed that the GaN powder was of single-phase wurtzite structure with a considerable fraction of structural defects such as twin and stacking faults. The IR spectrum showed that only the Ga–N stretch is present at 600 cm⁻¹. The EDX pattern of as-prepared product showed their ratio approximate to 1:1. Room temperature photoluminescence (PL) measurement exhibited the band-edge emission of GaN at about 390 nm and defect emission peak at 610 nm.     

A novel protocol to design TiO2-Fe2O3 hybrids with effective charge separation efficiency for improved photocatalysis

TiO₂-based heterogeneous photocatalysis has been widely considered as a promising technique for decontamination of water. Herein the hybrid of TiO₂ nanocrystals decorated Fe₂O₃ nanoparticles was successfully synthesized via a mild hydrothermal method, derived from favorable titanium glycolate and water-soluble Fe^II salt precursors. The composition and structure of the as-synthesized TiO₂-Fe₂O₃ hybrids were characterized by Powder X-ray diffraction (XRD), EDX mapping, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). The photocatalytic activity was evaluated by the decomposition of Rhodamine B in an aqueous solution under visible-light (λ > 420 nm). The results show that the TiO₂-Fe₂O₃ nanocomposite exhibits superior photocatalytic capability to the bare ones upon Rhodamine B degradation, owing to promoted photo-induced electrons and holes separation and migration on the basis of photoluminescence spectra, photocurrent measurements, and electrochemical impedance (EIS) spectroscopy.     

Synthesis of strontium zirconate as nanocrystals through a single step combustion process

Nanocrystals of strontium zirconium oxide (SrZrO₃), a high dielectric constant (ε′ = 60) ceramic, were synthesized using an auto-igniting combustion of a precursor solution containing metal ions, oxidant, and a fuel. Phase-purity and particulate properties of the as-prepared powder were examined using X-ray diffraction, differential thermal and thermogravimetric analyses, Fourier-transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopic techniques. As-prepared powder was single phase, crystalline, and composed of uniform particles with sizes of ∼ 15-25 nm. These nanocrystals were sintered to high density (∼ 98% of the theoretical density) at 1470 °C for 4 h.     

Morphology and phase selective synthesis of CuxO (x = 1, 2) nanostructures and their catalytic degradation activity

Cu_xO (x = 1, 2) nanocrystals have been synthesized by the composite-hydroxide-mediated approach. The obtained nanocrystals were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy, transmission electron microscopy, and UV–vis spectrum. The morphology of the nanocrystals changed from sphere-shaped nanostructures to flower-shaped nanostructures, and finally to nanowires associated with phase transformation from CuO to Cu₂O by increasing the temperature. The possible phase transformation mechanism was discussed. The catalytic degradation activity of the Cu_xO (x = 1, 2) nanocrystals to methyl orange was also investigated. The photocatalytic ability of the sphere-shaped nanostructures is much higher than that of the nanowires, owing to its absorption of wider range of light energy. This work provides a new facile synthesis route of Cu_xO (x = 1, 2) nanocrystals and suggests their possible application in organic pollutants removal.     

Preparation and characterization of LaNiO3 nanocrystals

Ten to twenty-three nanometers of LaNiO₃ nanocrystals were prepared by glycine combustion method using nickel nitrate and lanthanum nitrate as raw materials, glycine as gelating agent and fuel. The preparation process was monitored by thermogravimetric analysis and differential thermal analysis (TG-DTA); the final products were characterized by X-ray diffraction (XRD), electron diffraction (ED), high-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM). The effect of thermal treatment temperature on crystal size of the nanocrystals was studied and the activation energy of LaNiO₃ nanocrystals formation during calcinations was calculated to be 41.9 kJ/mol. Moreover, the interplanar distances of d₁₁₀ and d₁₀₁ measured from the TEM images were 0.272 and 0.363 nm, respectively, coinciding with the theoretical values.     

Preparation of new antimony(0)/polyaniline nanocomposites by a one-pot solution phase method

The new Sb(0)/PANI nanocomposite was successfully synthesized by a one-pot solution phase method. Sb(0) particles were first prepared by the reduction of SbCl₅ or SbCl₃ using t-BuONa-activated NaH in THF. A ligand exchange with aniline on t-BuONa-stabilized Sb(0) particles yielded aniline-stabilized particles. The Sb(0)/PANI nanocomposite was finally obtained by polymerizing aniline-stabilized Sb(0) particles by using ammonium persulfate. The morphology and the structure of the nanocomposite was examined by transmission electron microscopy (TEM), selected-area electron diffraction (SAED), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Results obtained show that the Sb(0) precursor has a great influence on the size and the crystallinity of Sb(0) nanoparticles dispersed in PANI.     

Spectromicroscopy Studies of Silicon Nanowires Array Covered by Tin Oxide Layers

The composition and atomic and electronic structure of a silicon nanowire (SiNW) array coated with tin oxide are studied at the spectromicroscopic level. SiNWs are covered from top to down with a wide bandgap tin oxide layer using a metal–organic chemical vapor deposition technique. Results obtained via scanning electron microscopy and X-ray diffraction showed that tin-oxide nanocrystals, 20 nm in size, form a continuous and highly developed surface with a complex phase composition responsible for the observed electronic structure transformation. The “one spot” combination, containing a chemically sensitive morphology and spectroscopic data, is examined via photoemission electron microscopy in the X-ray absorption near-edge structure spectroscopy (XANES) mode. The observed spectromicroscopy results showed that the entire SiNW surface is covered with a tin(IV) oxide layer and traces of tin(II) oxide and metallic tin phases. The deviation from stoichiometric SnO₂ leads to the formation of the density of states sub-band in the atop tin oxide layer bandgap close to the bottom of the SnO₂ conduction band. These observations open up the possibility of the precise surface electronic structures estimation using photo-electron microscopy in XANES mode.     

Capability of mechanical alloying and SPS technique to develop nanostructured high Cr,Al alloyed ODS steels

Abstract

Oxide dispersion strengthened (ODS) Fe alloys were produced by mechanical alloying (MA) with the aim of developing a nanostructured powder. The milled powders were consolidated by spark plasma sintering (SPS). Two prealloyed high chromium stainless steels (Fe–14Cr–5Al–3W) and (Fe–20Cr–5Al+3W) with additions of Y₂O₃ and Ti powders are densified to evaluate the influence of the powder composition on mechanical properties. The microstructure was characterised by scanning electron microscope (SEM) and electron backscattering diffraction (EBSD) was used to analyse grain orientation, grain boundary geometries and distribution grain size. Transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) equipped with energy dispersive X-ray spectrometer (EDX) were used to observe the nanostructure of ODS alloys and especially to observe and analyse the nanoprecipitates. Vickers microhardness and tensile tests (in situ and ex situ) have been performed on the ODS alloys developed in this work.     

Synthesis of sphere-like Co3O4 nanocrystals via a simple polyol route

A simple polyol method was developed to synthesize uniform sphere-like Co₃O₄ nanocrystals in ethylene glycol. Powder X-ray diffraction (XRD) and electron diffraction (ED) showed that the as-prepared sample was indexed as the cubic spinel structure. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that the Co₃O₄ nanocrystals were spherical with the crystallite size in the range of 90-110 nm. Infrared spectra and Raman spectra confirmed the formation of the Co₃O₄ nanocrystals. The magnetic properties of the Co₃O₄ nanocrystals were measured by using a superconducting quantum interference device (SQUID) magnetometer, which showed that the as-prepared sample exhibited a tiny hysteresis loop with the magnetization value of 2.4 emu/g and the coercivity of 110 Oe.