纳米钯/铁双金属颗粒对一氯乙酸的脱氯

为了提高零价铁对氯代有机物还原脱氯的性能,采用还原沉淀法制备了纳米钯/铁双金属颗粒.利用X射线衍射(XRD)、X射线荧光光谱(XRF)、扫描电子显微镜(SEM)、透射电镜(TEM)、以及BET-N2比表面积法对纳米钯/铁双金属颗粒进行了表征.结果表明,制备的纳米钯/铁双金属颗粒中Fe主要以α-Fe0形式存在.纳米钯/铁双金属颗粒的直径约为30～50nm,比表面积约51m2/g.纳米钯/铁双金属颗粒对一氯乙酸还原脱氯的脱氯率是还原铁粉和纳米铁粉对一氯乙酸还原脱氯的脱氯率的7.9倍和1.7倍.     

High resolution electron microscopy of bismuth oxides with perovskite layers

Layered bismuth oxides of the general formula (Bi₂O₂)²⁺ (A _n−1B_nO_3n+1)²⁻ whereA = Bi or Ba,B = Ti, Fe, W andn = number of perovskite layers have been investigated by high resolution electron microscopy. Lattice images obtained forn = 1 to 6 members show stacking of (n − 1) perovskite layers sandwiched between dark bands due to the (Bi₂O₂)²⁺ layers. It has been possible to resolve the perovskite layer structures in some of the oxides. A highly ordered structure is observed upto then = 3 member, whereas higher members show superstructures, dislocations and stacking faults arising from the side-stepping of (Bi₂O₂)²⁺ layers as well as ferroelectric domain walls. Contribution No. 73 from Materials Research Laboratory.     

Features of pulse substrate bias voltage generation with electron tubes

Features of pulse substrate bias voltage generation with electron tubes in different operation modes are considered. The overstressed mode with low anode voltage and return of electrons to the grid has practical significance at bias voltages in the kilovolt range under the conditions of large substrate current fluctuations. This mode ensures small bias voltage fluctuations and effective use of the primary DC voltage. When the substrate current spontaneously rises above the critical value, the tubes automatically decrease the bias voltage and suppress current spikes and arcing. Such approach may be used in PVD processes, for ion surface treatment and ion plasma immersion implantation.     

Surface modification of mild steel with Boron Carbide reinforcement by electron beam melting

We investigated the effect of surface hardening and micro-structural modifications in Mild steel (MS) with the addition of Boron Carbide, melted by thermionic electron beam. Boron Carbide in the form of powder was added by making grooves in MS samples to trap the molten solution for interaction with solid particles. These samples were irradiated by 10 KeV electron beam with variable beam current (50-100 mA). XRD confirmed the addition of Boron Carbide in the matrix and SEM indicated micro-structural changes introduced by the electron beam. Micro-structural modification further revealed that ferrites have been transformed into dendrites and pearlites have been refined as a result of re-solidified melt. This significantly has enhanced the surface hardness greater than 6-times compared to as received Mild steal.     

Characterization of Bi2S3 with different morphologies synthesized using microwave radiation

Bi₂S₃ with different morphologies (nanoparticles, nanorods and nanotubes) was synthesized using bismuth nitrate pentahydrate (Bi(NO₃)₃·5H₂O) and two kinds of sulfur sources (CH₃CSNH₂ and NH₂CSNH₂) in different solvents (water, ethylene glycol and propylene glycol) via a microwave radiation method at 180 W for 20 min. X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that all of the products are orthorhombic Bi₂S₃ phase of nanoparticles, nanorods and nanotubes, influenced by the sulfur sources and solvents. Formation mechanisms of the products with different morphologies are also proposed.     

Preparation of nanocrystalline bredigite powders with apatite-forming ability by a simple combustion method

Nanocrystalline bredigite (Ca₇MgSi₄O₁₆) powders were synthesized by a simple solution combustion method. Phase pure bredigite powders with particle sizes ranging from 234 to 463 nm could be obtained at a relatively low temperature of 650 °C. The apatite-forming ability of the bredigite powders was examined by soaking them in a stimulated body fluid. The compositional and morphological changes of the powders before and after soaking were analyzed by X-ray diffraction and scanning electron microscopy and the results showed that hydroxyapatite was formed after soaking for 4 days.     

Microstructure and mechanical properties of nickel based superalloy IN718 produced by rapid prototyping with electron beam melting (EBM)

Abstract

A nickel alloy of a composition similar to that of the nickel based superalloy Inconel alloy 718 (IN718) was produced with the electron beam melting (EBM) process developed by Arcam AB. The microstructures of the as processed and heat treated material are similar to that of conventionally produced IN718, except that the EBM material showed some porosity and the δ phase did not dissolve during the solution heat treatment because the temperature of 1000°C apparently was too low. Mechanical testing of the layer structured material, parallel and perpendicular to the built layers, revealed sufficient strength in both directions. However, it showed only limited elongation when tested perpendicular to the built layers due to local agglomerations of pores. Otherwise, data for the hardness, Young’s modulus, 0·2% yield tensile strength and ultimate tensile strength match those recommended for IN718.     

Sodium carboxylate effect of non-cross-linked hydrogel on plasma-induced radical formation as studied by electron spin resonance

The possibility of refining the functionality of vinyl alcohol-sodium acrylate copolymer, P(VA-AANa), regarding its curative effect on chemo-embolic agents by plasma treatment, was examined, We have carried out argon plasma-irradiation onto the P(VA-AANa) microsphere and the surface radicals formed were studied by ESR and compared with those of vinyl alcohol-acrylic acid copolymer, P(VA-AA), as well as its respective component homopolymer, PVA, PAA and its sodium salt (PAANa). It was found that the ESR spectra have shown a vast difference in pattern between P(VA-AANa) and P(VA-AA), demonstrating the strong sodium carboxylate effect on the nature of plasma-induced surface radical formation resulting from the difference in the surface morphology between P(VA-AANa) and P(VA-AA).     

自吸水性超强吸水剂的研究

通过自吸水性化合物甘油与淀粉接枝丙烯酸或丙烯酰胺相结合,制备了两种可以从空气中吸收水分的自吸水性超强吸水剂,并对其吸水性能进行了研究.结果表明:树脂的合成条件对吸水率有很大影响,反应3h,温度70℃,引发剂浓度6×10-4mol/L,甘油的质量分数为40%时,制得的自吸水性超强吸水剂吸水能力最强;甘油-淀粉丙烯酰胺体系的自吸水能力优于甘油-淀粉丙烯酸体系的自吸水能力;泥土与超强吸水剂混合后可以自动从空气中吸收水分,与甘油-淀粉-丙烯酰胺混合的土壤,放置20d后其自吸水率可达14.8%.     

Utilization of copper phthalocyanine and bathocuproine as an electron transport layer in photovoltaic cells with copper phthalocyanine/buckminsterfullerene heterojunctions: Thickness effects on photovoltaic performances

In this work, copper phthalocyanine (CuPc) and bathocuproine (BCP) were used as electron transport layers (ETL) in organic photovoltaic (PV) cells with a structure of indium-tin-oxide/CuPc/C60/ ETL/Al. It was found that PV performance was sensitive to the ETL thickness. A complete coverage of ETL on the C60 film was essential to avoid an insulative C60/Al contact. ETL thickness of 6 nm resulted in optimal PV performance. The PV cells with BCP layers of 2-10 nm demonstrated good PV performance due to efficient electron transport from C60 to Al cathode. Similar result was obtained from the devices with CuPc ETL. However, thicker ETL resulted in considerable lose in PV performance. In both cases, different mechanisms responsible for the dependence of PV performance on ETL thickness are discussed.     

Growth behavior of CVD diamond films with enhanced electron field emission properties over a wide range of experimental parameters

In this study, diamond films were synthesized on silicon substrates by microwave plasma enhanced chemical vapor deposition (CVD) over a wide range of experimental parameters. The effects of the microwave power, CH₄/H₂ ratio and gas pressure on the morphology, growth rate, composition, and quality of diamond films were investigated by means of scanning electron microscope (SEM), X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). A rise of microwave power can lead to an increasing pyrolysis of hydrogen and methane, so that the microcrystalline diamond film could be synthesized at low CH₄/H₂ levels. Gas pressure has similar effect in changing the morphology of diamond films, and high gas pressure also results in dramatically increased grain size. However, diamond film is deteriorated at high CH₄/H₂ ratio due to the abundant graphite content including in the films. Under an extreme condition of high microwave power of 10 kW and high CH₄ concentration, a hybrid film composed of diamond/graphite was successfully formed in the absence of N₂ or Ar, which is different from other reports. This composite structure has an excellent measured sheet resistance of 10–100 Ω/Sqr. which allows it to be utilized as field electron emitter. The diamond/graphite hybrid nanostructure displays excellent electron field emission (EFE) properties with a low turn-on field of 2.17 V/μm and β = 3160, therefore it could be a promising alternative in field emission applications.     

Ionic-liquid-assisted synthesis of YF3 with different crystalline phases and morphologies

YF₃ with different crystalline phases and morphologies have been prepared via a facile hydrothermal route assisted by imidazolium ionic liquids 1-butyl-3-methylimidazolium tetrafluoroborate (C₄mimBF₄) or 1-butyl-3-methylimidazolium hexafluorophosphate (C₄mimPF₆). The microstructures and morphologies of YF₃ particles were characterized by X-ray powder diffraction, X-ray photoelectron spectra (XPS), transmission electron microscopy (TEM), high resolution electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM). Cubic and orthorhombic YF₃ were selectively synthesized by adjusting the molar ratio of the reagents and using C₄mimBF₄ as the fluoride source, while only orthorhombic YF₃ was obtained using C₄mimPF₆, indicating that the crystalline phases and morphologies of the products were significantly influenced by fluoride source and reaction media.     

氢在不同成分和显微组织的Mg-Ni合金电极中的扩散能力研究

采用机械球磨的方法,制备了不同成分和显微组织的MgxNi(x=1%、1.5%、2%(原子分数))合金粉,并采用X射线衍射(XRD)和扫描电子显微镜的方法研究了Mg/Ni比对机械球磨过程中Mg-Ni合金粉末组织结构演变的影响。在不同的电位扫描速度下,对具有不同Mg/Ni比和显微组织结构的Mg-Ni合金电极循环伏安曲线进行了测量,并由此计算出了氢在这些电极中的扩散系数,分析了合金成分和显微组织对Mg-Ni合金电极中氢扩散能力的影响。其结果表明,降低Mg/Ni比,能提高Mg-Ni合金在球磨过程中非晶相的形成能力,Mg-Ni和Mg1.5Ni合金获得完全非晶相的球磨时间分别是120和160h。在由细小、分散并且完全非晶态的Mg-Ni合金颗粒制备的电极中,氢表现出较强的扩散能力,其扩散系数为1.98×10-8cm2/s。     

Investigating the blending of reclaimed asphalt with virgin materials using rheology,electron microscopy and computer tomography

The nature of blending of virgin materials with reclaimed asphalt pavement (RAP) has been investigated using a multi scale approach using the dynamic shear rheometer (DSR), electron microscopy and computer tomography (CT). In order to simplify the visualization of the blending of the virgin and reclaimed materials five specially engineered hot asphalt mixtures were produced incorporating large mineral fraction (8/11 mm) of virgin aggregates and small fraction (2/4 mm) from RAP mixed with virgin bitumen. The complex modulus and phase angle of reclaimed binder from the blended mixtures were found to be between that of RAP and virgin binder. The CT slices of compacted cylindrical samples (150 mm diameter × 120 mm height) could incorporate the effect of compaction on the blending. They show lumped regions with virgin large aggregates as well as lumped regions of RAP aggregates. Using micro CT the spatial distribution of the different binders was investigated at the micro-scale. Millimeter size distinct clusters of virgin binder and clusters of RAP binder could be distinguished. The existence of RAP binder next to large virgin aggregates indicated the migration of the old RAP binder from the RAP aggregates to the virgin aggregates. From these CT images, it was not possible to verify if blending between the virgin and old binders occurred. Using electron microscopy micro-crack formations in the zone between old and new binder were identified suggesting weak spots that could lead to larger crack formation and propagation. However, using energy-dispersive X-ray spectroscopy good qualitative distribution of titanium dioxide tracer in the virgin binder in the mixture could be seen, indicating good blending at the investigated location. Hence, the results show that blending is not homogeneous throughout the sample. Some locations show good blending whereas other locations appear non-blended with micro-cracks forming at the binder boundaries.     

Synthesis and characterization of a novel poly(p-phenylenevinylene) derivative containing dibenzothiophene-5,5-dioxide moiety in the main chain with high electron affinity

We synthesized poly(2,8-dibenzothiophene-5,5-dioxide-vinylene-alt-1,4-phenylene-vinylene) (DD-PPV) (oligomer) by the traditional Wittig condensation and characterized it with IR, NMR, UV-vis etc. It is thermally stable and soluble in high polar solvents. Its UV-vis absorption and photoluminescence spectra in N,N-dimethyl-formamide solution show peaks at 369 and 457 nm, respectively. Its fluorescence quantum efficiency in solution is 75%. Its electron affinity is 3.17 eV. The band gap is 2.88 eV. Single-layer light-emitting diode device indium-tin oxide glass/DD-PPV/Aluminum emits greenish blue and the turn-on voltage is approximately 12 V.     

The influence of different porogens with halogen substituents on the pore structure of polydivinylbenzene beads

Polydivinylbenzene (PDVB) beads with high surface area and porosity were prepared via suspension polymerization in the presence of solvents with halogen substituents as porogens. The porogens employed in the present work were p-dichlorobenzene, chlorobenzene, bromobenzene, benzyl chloride, and tetrachloroethane. The porogens were used in a 1/1 volume ratio with divinylbenzene (DVB). As predicted from previous knowledge of porogen with halogen substituents possessing strong capacity to construct porosity, the surface area of PDVB beads prepared with the above porogens reached 647.1–744.6 m² g⁻¹, which mainly depended on the difference of solubility parameter of the porogens and PDVB networks. The smaller the difference, the larger the surface area of PDVB beads was. Overall, research results of the present study indicated that in comparison with other types of porogen, solvent with halogen substituent could generate larger surface area and construct higher porosity in PDVB beads.     

Synthesis and characterization of microporous titanosilicate ETS-10 obtained with different Ti sources

Titanosilicate ETS-10 crystals were prepared by hydrothermal synthesis varying Ti source (TiCl₃ and commercial TiO₂-anatase), time in autoclave and seeding with previously prepared ETS-10 crystals. The crystalline powders were characterized by X-ray diffraction, N₂ adsorption, thermogravimetric analysis, and scanning and transmission electron microscopies. Control of the particle size of ETS-10 crystals ranging from 0.32 μm × 0.41 μm to 16.4 μm × 32.5 μm was successfully achieved varying the seeding and synthesis conditions. In particular, it was found that the use of TiO₂-anatase alone or together with TiCl₃ promotes heterogeneous primary nucleation. Transmission electron microscopy demonstrated that the largest crystals obtained here were twinned.     

不同形貌的甲酸掺杂聚苯胺的电容性能

采用界面聚合法,用FeCl3作氧化剂,不同浓度的HCOOH做掺杂剂,制备了不同形貌聚苯胺纳米材料,并用扫描电子显微镜(SEM),X射线衍射(XRD)对聚苯胺的结构和形貌进行了表征。以聚苯胺为活性物质制备电极,1mol/LH2SO4水溶液为电解液组装超级电容器,通过循环伏安法和恒电流充放电技术研究了其电化学性能。结果表明,通过控制HCOOH的浓度可以得到不同形貌的HCOOH掺杂的聚苯胺纳米材料;其中纤维状的聚苯胺作为电极材料的超级电容器在15mA/cm2放电电流下,其比电容为292.2F/g,500次循环后容量仍维持在200.6F/g,比电容保持率为68.7%。     

Ultrafine 316 L stainless steel particles with frozen-in magnetic structures characterized by means of electron backscattered diffraction

Electron Backscatter Diffraction (EBSD) studies clearly revealed a different crystallographic structure of the smallest particle size fraction of gas-atomized AISI 316 L stainless steel powder (< 4 μm) compared with larger sized fractions of the same powder (< 45 μm). Despite similar chemical compositions, the predominating structure of the smallest particle size fraction was ferritic (i.e., has ferromagnetic properties) whereas the larger sized particle fractions and massive 316 L revealed an expected austenitic and non-magnetic structure. From these findings, it follows that direct magnetic separation can be applied to separate very fine sized particles. These structural differences explain previously observed dissimilarities from corrosion and metal release perspectives.     

Role of rigid nanoparticles and CTBN rubber in the toughening of epoxies with different cross-linking densities

Experimental investigations were conducted to characterize the fracture behaviours of Bisphenol A diglycidyl ether (DGEBA) epoxies modified with rigid nanoparticles (nanosilica or halloysite) and a reactive liquid carboxylterminated butadiene–acrylonitrile (CTBN) liquid rubber to identify toughening mechanisms and toughenability in the cured epoxies with different cross-linking densities. The epoxy was cured using three different hardeners, a heterocyclic amine (piperidine), a cycloaliphatic polyamine (Aradur 2954) and an aromatic amine [4,4′-Diaminodiphenyl sulfone (DDS)] to form nanocomposites with different cross-linking densities. It was found that both the hybrid particles, nanosilica with CTBN rubber and halloysite with CTBN rubber, were effective additives that clearly increased the fracture toughness of the three epoxy composites. In particular, the use of halloysite nanoparticles as additives for the epoxies showed greater potential than nanosilica to increase strength and modulus due to the reinforcing effect of the halloysite nanotubes (HNTs). The epoxy systems cured with the hardeners (Aradur 2954 and DDS), which generated relatively high cross-linking densities, evidenced inferior toughenability of the hybrid particles, compared with the epoxy systems cured using the hardener (piperidine), which produced lower cross-linking densities. The CTBN rubber formed dissimilar domains in different epoxy systems, features which were attributed to the different toughenability of the hybrid particles in the systems due to variations in the dominant toughening mechanisms involved.