Influence of the solvent on ultrasonically produced SbSI nanowires

The influence of the substitution of methanol in place of ethanol during the ultrasonic production of antimony sulfoiodide (SbSI) nanowires is presented. The new technology is faster and more efficient at temperatures greater than 314 K. The products were characterized by using techniques such as powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDXA), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), optical diffuse reflection spectroscopy (DRS) and IR spectroscopy. The coexistence of Pna2₁ (ferroelectric) and Pnam (paraelectric) phases at 298 K was observed in the SbSI nanowires produced in methanol. The methanol decomposes during the sonication or due to the adsorption process on SbSI nanowires.     

Infrared analysis of nano organic particles produced in laminar flames

In this work we present the first infrared investigation of nano-sized organic carbon (NOC) particles produced in premixed laminar ethylene flames. We analyzed the chemical transformation of NOC when the combustible/oxidant ratio (C/O) passed from lean to slightly sooting conditions. We also demonstrate the increase of the aromatic character for samples under thermal treatment. The analysis of the infrared spectra clearly shows the persistence of this material after soot inception. PACS 33.20.Ea; 82.33.Vx     

Membrane cleaning with ultrasonically driven bubbles

A laboratory filtration plant for drinking water treatment is constructed to study the conditions for purely mechanical in situ cleaning of fouled polymeric membranes by the application of ultrasound. The filtration is done by suction of water with defined constant contamination through a membrane module, a stack of five pairs of flat-sheet ultrafiltration membranes. The short cleaning cycle to remove the cake layer from the membranes includes backwashing, the application of ultrasound and air flushing. A special geometry for sound irradiation of the membranes parallel to their surfaces is chosen. Two frequencies, 35 kHz and 130 kHz, and different driving powers are tested for their cleaning effectiveness. No cleaning is found for 35 kHz, whereas good cleaning results are obtained for 130 kHz, with an optimum cleaning effectiveness at moderate driving powers. Acoustic and optic measurements in space and time as well as analytical considerations and numerical calculations reveal the reasons and confirm the experimental results. The sound field is measured in high resolution and bubble structures are high-speed imaged on their nucleation sites as well as during their cleaning work at the membrane surface. The microscopic inspection of the membrane surface after cleaning shows distinct cleaning types in the cake layer that are related to specific bubble behaviour on the membrane. The membrane integrity and permeate quality are checked on-line by particle counting and turbidity measurement of the permeate. No signs of membrane damage or irreversible membrane degradation in permeability are detected and an excellent water permeate quality is retained.     

Comparison of simulated X-ray conversion efficiency of laser produced iron plasma with experimental results

X-ray resonance lines between 11 Å and 17 Å emitted from iron plasmas created by a modest KrF laser have been simulated by modifying the atomic and hydrodynamic code EHYBRID. Free–free and free–bound emission from the Si-, Al-, Mg-, Na-, Ne- and F-like ions is calculated in the simulation. In the original experiments, a KrF laser (249 nm wavelength) with focused irradiances between 1×10¹² W/cm² and 1×10¹⁵ W/cm² was focused on iron targets. The laser pulse duration was varied between 10 ps and 20 ns. We have calculated X-ray conversion efficiencies to be, for example, 0.5% over 2 sr for 2×10¹³ W/cm² and 20 ns pulse duration, in good agreement with experimental measurements. The simulation of X-ray emission is also presented for an experiment where a train of eight 7 ps KrF laser pulses is incident onto an iron target. PACS 52.50.Jm; 52.38.Ph; 52.65.Kj; 52.30.Ex; 32.30.Rj     

Iron oxide and iron carbide particles produced by the polyol method

Iron oxide (γ-Fe₂O₃) and iron carbide (Fe₃C) particles were produced by the polyol method. Ferrocene, which was employed as an iron source, was decomposed in a mixture of 1,2-hexadecandiol, oleylamine, and 1-octadecene. Particles were characterized using Mössbauer spectroscopy, X-ray diffraction, and transmission electron microscopy. It was found that oleylamine acted as a capping reagent, leading to uniform-sized (12-16 nm) particles consisting of γ-Fe ₂O₃. On the other hand, 1-octadecene acted as a non-coordinating solvent and a carbon source, which led to particles consisting of Fe₃C and α-Fe with various sizes.     

Aspects of ultrasonically assisted transesterification of various vegetable oils with methanol

The batch transesterification of vegetable oil with methanol, in the presence of potassium hydroxide as catalyst, by means of low frequency ultrasound (40 kHz) was studied with the aim of gaining more knowledge on intimate reaction mechanism. The concentration of fatty acid methyl esters, of mono-, di- and triglycerides of the actual reaction mixture were determined at short reaction time by HPLC. The effect of ultrasounds on the lipids transesterification correlated with triglyceride structures is discussed. It was found that under ultrasonic activation the rate-determining reaction switches from DG-->MG (classical mechanic agitation) to MG+ROH-->Gly+ME (ultrasonically driven transesterification).     

Mössbauer and EXAFS studies of amorphous iron produced by thermal decomposition of carbonyl iron in liquid phase

Decomposition of iron carbonyl Fe(CO)₅ and Fe₂(CO)₉ in liquid phase gave amorphous and crystalline iron powders in the absence and presence of catalyst, respectively. The hyperfine fields were large in amorphous phases prepared from Fe(CO)₅ than from Fe₂(CO)₉. Crystalline iron, iron carbide and a trace amount of Fe₃O₄ were detected in the decomposition products of the amorphous phase prepared from Fe(CO)₅, and iron carbide was mainly included in the decomposition products of the amorphous phase prepared from Fe₂(CO)₉.     

Synthesis of nano onion-like fullerenes by chemical vapor deposition using an iron catalyst supported on sodium chloride

Nano-carbon materials were synthesized by the catalytic decomposition of acetylene at 420 °C using iron supported on sodium chloride as catalyst. The catalysts contain about 0.3, 1.6, 3.3, and 5.2 wt% iron. The samples were examined by scanning and transmission electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. The results show that nano onion-like fullerenes (NOLFs) surrounding an Fe₃C core were obtained using the catalyst containing 0.3 wt% iron. These had a structure of stacked graphitic fragments, with diameters in the range 15–50 nm. When the product was further heat treated under vacuum at 1,100 °C, NOLFs with a clear concentric graphitic layer structure were obtained. The growth mechanism of NOLFs encapsulating metallic cores is suggested to be in accordance with a vapor–solid growth model.     

Magnetic iron oxide nanopowders produced by CO2 laser evaporation

Magnetic iron oxide nanopowders were produced with the laser evaporation technique under normal process gas pressure. In addition, the generated particles were coated in situ with stearic acid and separated on magnets. The methods and the used laboratory setup are briefly described. Influences of essential process conditions, particularly the use of continuous and pulsed laser radiation as well as the properties of the process gas, were experimentally investigated. The produced nanopowders were analysed with TEM, XRD, and magnetic measurements and confirmed the in-principle suitability of the presented method.     

Spin-polarizing properties of heterostructures with magnetic nano elements

The problem of electron resonant and non-resonant scatterings on two magnetized barriers is studied in the one-dimension. The transfer-matrix is built up to exactly calculate the coefficient of the electron transmittance through the system of two magnetic barriers with non-collinear magnetizations. The polarization of the transmitted electron wave for resonance and non-resonance transmittances is calculated. The transmittance coefficient and spin polarization can be drastically enhanced and controlled by the angle between the barrier magnetizations.     

Surface science studies of environmentally relevant iron (oxy)hydroxides ranging from the nano to the macro-regime

In this prospective, new developments in the study of the structure and reactivity of iron oxyhydroxides are reviewed. These materials are of particular interest, since their surfaces control an extraordinary amount of environmental chemistry. Understanding the environmental interfaces at a molecular level often appears to be a daunting scientific endeavor at first glance. Surfaces of interest range from the nano to micron regime and appear in the environment in varying shapes and sizes. Often the powerful suite of vacuum-based surface science tools are not applicable, since the surfaces of environmental particles can vary from amorphous to semi-crystalline and their surface reactivity is often affected by varying levels of surface hydration. However, the introduction of new and powerful surface probes and advancements in computational chemistry are allowing surface scientists to shed light on these hidden interfaces and how they control environmental chemistry.     

Ultrasound-assisted heterogeneous activation of persulfate by nano zero-valent iron (nZVI) for the propranolol degradation in water

This study investigated the degradation of propranolol (PRO), a beta (β)-blockers, by nano zero-valent iron (nZVI) activated persulfate (PS) under ultrasonic irradiation. Effects of several critical factors were evaluated, inclusive of PS concentration, nZVI dosage, ultrasound power, initial pH, common anions, and chelating agent on PRO degradation kinetics. Higher PS concentration, nZVI dosage and ultrasound power as well as acidic pH favored the PRO degradation. Conversely, anions and chelating agent took on the inhibitory effect towards PRO degradation to different extents. Furthermore, the variations of morphology and surface composition of nZVI before and after the reaction were characterized by TEM, XRD and XPS. Finally, on the basis of identified degradation intermediates by LC/MS/MS analysis, this work tentatively proposed the degradation pathways. These encouraging results suggest that US/nZVI/PS process is a promising strategy for the treatment of PRO-induced water pollutant.     

Protection against corrosion of iron alloys by aluminized coatings produced using two different processes

Aluminized coatings were produced on iron by means of two different processes: electron beam deposition under UHV of Al on iron samples previously covered with ⁵⁷Fe films, and hot-dipping of iron samples in molten aluminium. Aluminized samples were submitted to thermal treatments in order to promote interdiffusion at the Fe–Al interface and favour the formation of Fe–Al intermetallic compounds of composition suitable to protect the underlying iron from oxidation. Phase composition, structure and morphology of both as deposited and thermally treated coatings were characterized by means of X-ray diffraction, Mössbauer spectroscopy and metallographic techniques. Significant differences among the effects of the Fe–Al interdiffusion occurring for Al layers produced with the two processes are pointed out and discussed.     

Development of recrystallization in various ultrafine structures produced in iron by severe plastic deformation

It has been shown that the behavior of iron upon heating depends on the type of the ultrafine structure produced in iron upon deformation by shear under pressure. The type of the structure is related to the multistage development of deformation.     

掺杂纳米材料光纤的研制

将纳米技术与光纤技术相结合,利用改进的化学气相沉积法(MCVD)制作纳米级InP薄膜内包层光纤及在普通单模光纤纤芯中掺杂纳米级InP粒子的新型光纤,前者单位长度放大系数最大达到15.35dB/m,能在较短的长度上对信号光起到放大作用,便于集成化;后者经实验证实其纤芯具有光波导传输性能.两种新型高非线性光纤在光通信器件中的具有应用前景.     

Evanescent-wave photoacoustic spectroscopy with optical micro/nano fibers

We demonstrate gas detection based on evanescent-wave photoacoustic (PA) spectroscopy with tapered optical fibers. Evanescent-field instead of open-path absorption is exploited for PA generation, and a quartz tuning fork is used for PA detection. A tapered optical fiber with a diameter down to the wavelength scale demonstrates detection sensitivity similar to an open-path system but with the advantages of easier optical alignment, smaller insertion loss, and multiplexing capability.     

1064 nm Nd:YAG激光诱导铁等离子体特征参数的研究

利用1064 nm Nd:YAG激光器研究了激光诱导铁条等离子体的特征参数。为了减小测量误差和谱线自发辐射跃迁几率不确定性带来的计算误差,采用改进的迭代Boltzmann方法精确求解铁等离子体的电子温度为8058 K。Lorentz函数拟合Fe I 376.553 nm得到等离子体的电子数密度为8.71017 cm-3。分析表明等离子体的加热机制主要是逆轫致过程,其吸收系数是0.14 cm-1。实验数据证实激光诱导铁等离子体处于局部热力学平衡状态和光学薄状态。     

Compositional and structural characterization of nanoporous films produced by iron anodizing in ethylene glycol solution

We report on the composition and morphology of as-grown anodic oxide films onto the iron surface in an ethylene glycol solution containing some NH₄F and H₂O by anodizing under direct current bias. Decrease in the content of NH₄F and the temperature of electrolyte allow us to form either nanochannel or nanotubular films over a larger potential window, ca. from 30 to 100 V. By this way, the films in thickness of up to10 μm have been formed. Mössbauer spectra recorded at room to cryogenic temperatures under conversion electron and transmission modes revealed the formation of lepidocrocite (γ-FeOOH) film containing some Fe(OH)₂ and/or FeF₂·4H₂O. An increase in anodizing voltage results in fabrication of more porous and less Fe(II) compounds containing films.     

1064 nm Nd:YAG激光诱导铁等离子体特征参数的研究

利用1064 nm Nd:YAG激光器研究了激光诱导铁条等离子体的特征参数。为了减小测量误差和谱线自发辐射跃迁几率不确定性带来的计算误差,采用改进的迭代Boltzmann方法精确求解铁等离子体的电子温度为8058 K。Lorentz函数拟合Fe I 376.553 nm得到等离子体的电子数密度为8.71017 cm-3。分析表明等离子体的加热机制主要是逆轫致过程,其吸收系数是0.14 cm-1。实验数据证实激光诱导铁等离子体处于局部热力学平衡状态和光学薄状态。