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X-ray Spectroscopy (x-ray + spectroscopy)
Kinds of X-ray Spectroscopy Selected AbstractsThe effect of alloying elements on the crystallization behaviour and on the properties of galvanized coatingsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 1 2004G. Vourlias Abstract The influence of the alloying elements on the interface reactions of zinc coatings during the galvanization process was examined. These reactions affect the crystallization and the structure and properties of the outer layer of the coatings. Depending on the type and concentration of the alloying additions in the galvanizing bath differences were induced in the crystallization process of the Fe-Zn phases. It was found that both the concentration and the distribution of the alloying elements played an important role in the growth of the phases. The formation of the phases and the distribution of the alloying elements in the coatings were determined using X-Ray diffraction (XRD) and Scanning Electron Microscopy (SEM) associated with an Energy Dispersive X-Ray Spectroscopy (EDS) analysis. Finally the behaviour of the galvanized coatings was examined under accelerated salt spray corrosion conditions. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Active Metal Electrode,Oxide Interface in Gas Sensor Operation Probed by In Situ and Time-Resolved X-Ray SpectroscopyCHEMPHYSCHEM, Issue 1 2010Aleksander Gurlo Dr. The feasibility of the in situ and operando methodology in studying the chemical and electronic phenomena associated with an active metal electrode,oxide interface in metal-oxide-based gas sensors (picture) is demonstrated. It is experimentally verified that the Pt electrodes in metal-oxide based gas sensors are partially oxidised and that the oxidised Pt electrodes contribute to overall sensing performance. [source] Filling of carbon nanotubes for bio-applicationsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 11 2007S. Costa Abstract Carbon nanotubes (CNT) provide a smart carrier system on the nanometer scale. The system can be used as a template for ferromagnetic fillers. Such a molecular hybrid is a promising potential candidate for the controlled heating of tumour tissue at the cellular level. This is a key reason why it is important to optimize the synthesis route of metal filled carbon nanotubes with regards bulk scale synthesis and purity. In the current study we present multiwalled carbon nanotubes filled with ,-iron phase (Fe-MWCNT). The influence of acid treatment on the stability of the filling and the sample purity is also presented. High resolution transmission microscopy, its Energy dispersive X-Ray spectroscopy (EDX) and electron energy-loss spectroscopy (EELS) modes have been applied for the analysis of the morphology and chemical composition of the samples. The phase of iron nanowires encapsulated into the carbon nanotubes was determined with selected area electron diffraction (SAED) on a local scale. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Mechanical and tribological characterization of CNx films deposited by d.c. magnetron sputteringPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2007L. Ipaz Abstract Carbon nitride (CNx) thin films were deposited onto silicon and steel substrates at 400 °C from a carbon target by d.c. magnetron sputtering system. The composition, structural, and mechanical properties of deposited films were investigated as a function of argon/nitrogen concentration and sputtering power, by means of Energy Dispersive X-ray Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy (RS), and nanoindentation. The EDS and Elastic Forward Analisys Analysis (EFA) showed that the nitrogen concentration in the CNx deposited films varied between 16% and 28% at depending on nitrogen concentrations in argon/nitrogen gas mixture, and deposition power. FTIR analysis indicated the presence of 2266 and 2278 cm,1 stretching peaks associated with CN triple bonds of nitriles and isocyanides, 1640 cm,1 and 1545 cm,1 associated with the C=C and C=N bonds. The thickness of the CNx deposited films varied between 0.4 and 0.8 µm at different sputtering powers. The hardness and Young's modulus were investigated by depth sensing nanoindentation method. The obtained hardness and Young's modulus increased from 4 to 17 GPa, and from 50 to 170 GPa, respectively; when the nitrogen content in the deposited films diminished between 28 and 12%. On the other hand, the friction and wear tests were done using a pin-on-disc tribometer. The friction tests showed values of 0.05 and 0.4 in dry air and humid atmosphere; respectively. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] On-line optical and X-ray spectroscopies with crystallography: an integrated approach for determining metalloprotein structures in functionally well defined statesJOURNAL OF SYNCHROTRON RADIATION, Issue 5 2008Mark J. Ellis X-ray-induced redox changes can lead to incorrect assignments of the functional states of metals in metalloprotein crystals. The need for on-line monitoring of the status of metal ions (and other chromophores) during protein crystallography experiments is of growing importance with the use of intense synchrotron X-ray beams. Significant efforts are therefore being made worldwide to combine different spectroscopies in parallel with X-ray crystallographic data collection. Here the implementation and utilization of optical and X-ray absorption spectroscopies on the modern macromolecular crystallography (MX) beamline 10, at the SRS, Daresbury Laboratory, is described. This beamline is equipped with a dedicated monolithic energy-dispersive X-ray fluorescence detector, allowing X-ray absorption spectroscopy (XAS) measurements to be made in situ on the same crystal used to record the diffraction data. In addition, an optical microspectrophotometer has been incorporated on the beamline, thus facilitating combined MX, XAS and optical spectroscopic measurements. By uniting these techniques it is also possible to monitor the status of optically active and optically silent metal centres present in a crystal at the same time. This unique capability has been applied to observe the results of crystallographic data collection on crystals of nitrite reductase from Alcaligenes xylosoxidans, which contains both type-1 and type-2 Cu centres. It is found that the type-1 Cu centre photoreduces quickly, resulting in the loss of the 595,nm peak in the optical spectrum, while the type-2 Cu centre remains in the oxidized state over a much longer time period, for which independent confirmation is provided by XAS data as this centre has an optical spectrum which is barely detectable using microspectrophotometry. This example clearly demonstrates the importance of using two on-line methods, spectroscopy and XAS, for identifying well defined redox states of metalloproteins during crystallographic data collection. [source] Experiments on single levitated particles: a novel approach for investigations of electronic properties of structured II-VI-semiconductor nanoparticles in selected environmentsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2007C. Graf Abstract A novel approach for investigations of the electronic structure of II-VI semiconductor nanoparticles in selected environments is presented. CdSe/ZnS core shell nanoparticles are dispersed in a liquid non-volatile siloxane graft/block copolymer and injected in an electrodynamic trap, where a single liquid microdroplet is stably stored under ultra high vacuum conditions. In this way, it is possible to investigate quantum dots by soft X-ray spectroscopies in a liquid environment, which is not influenced by any outer surface. NEXAFS spectra of stored nanoparticles were recorded at the Zn 2p-, S 2p-, and Cd 3d-edge by measuring X-ray excited optical luminescence or the element-selective charging current of single, trapped microdroplets. The spectra are compared to those of similar CdSe/ZnS nanoparticles, which are dispersed in a controlled way in solid silica colloids as well as to those of matrix materials. An analysis of the data reveals that the electronic structure of the ZnS shell is significantly influenced by the outer functionalization and the dispersive media whereas the electronic structure of the core is shown to be independent from the surroundings. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effect of thorium on the growth and capsule morphology of BradyrhizobiumENVIRONMENTAL MICROBIOLOGY, Issue 10 2003Mónica Santamaría Summary The thorium effect on Bradyrhizobium growth was assayed in liquid media. Th4+ inhibited the growth of Bradyrhizobium (Chamaecytisus) BGA-1, but this effect decreased in the presence of suspensions of live or dead bacterial cells. Th4+ induced the formation of a gel-like precipitate when added to a dense suspension of B. (Chamaecytisus) BGA-1 cells. Viable Bradyrhizobium cells remained in suspension after precipitate formation. Thorium was recovered in the precipitate, in which polysaccharide, lipopolysaccharide and proteins were also found. After Th4+ addition, the morphology of B. (Chamaecytisus) BGA-1 or Bradyrhizobium japonicum USDA 110 sedimented cells studied by scanning electron microscopy changed from an entangled network of capsulated bacteria to uncapsulated individual cells and an amorphous precipitate. Energy-dispersive X-ray spectroscopy showed that thorium was mainly in the amorphous fraction. Precipitate was also formed between B. (Chamaecytisus) BGA-1 and Al3+, which was also toxic to this bacterium. Precipitate induced by Th4+ or Al3+ was found in all Bradyrhizobium and Sinorhizobium strains tested, but not in Rhizobium, Salmonella typhimurium, Aerobacter aerogenes or Escherichia coli. These results suggest a specific defence mechanism based on metal precipitation by extracellular polymers. [source] Synthesis and Characterization of Single-Crystalline Lanthanum Fluoride with a Ring-Like NanostructureEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2009Yang Tian Abstract LaF3 ring-like nanostructures with a diameter of less than 2 ,m have been fabricated by a facile, effective, and environmentally friendly molten salt synthesis route in which NaNO3 and KNO3 (2:1 molar ratio) act as reaction media and the rare-earth nitrate and NaF as precursor. X-ray diffraction, TEM, HR-TEM, energy dispersive X-ray spectroscopy, and photoluminescence spectroscopy are all used to characterize the as-prepared samples. Experiments peformed with different reaction times indicate that a central-etching of the plates from the inner part towards the edge during nanocrystal growth plays a key role in the formation of LaF3 nanorings since no other templates/surfactants are present in our system. Additionally, the luminescence properties of LaF3 nanorings doped with Eu3+ cation have been investigated andcompared with those of bulk materials and nanoparticles with a size of approximately 50 nm. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Tin-containing fluoride solutions as anti-erosive agents in enamel: an in vitro tin-uptake, tissue-loss, and scanning electron micrograph studyEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 4 2009Nadine Schlueter Tin-containing fluoride solutions can reduce erosive tissue loss, but the effects of the reaction between tin and enamel are still not clear. During a 10-d period, enamel specimens were cyclically demineralized (0.05 M citric acid, pH 2.3, 6 × 5 min d,1) and remineralized (between the demineralization cycles and overnight). In the negative-control group, no further treatment was performed. Three groups were treated (2 × 2 min d,1) with tin-containing fluoride solutions (400, 1,400 or 2,100 ppm Sn2+, all 1,500 ppm F,, pH 4.5). Three additional groups were treated with test solutions twice daily, but without demineralization. Tissue loss was determined profilometrically. Energy-dispersive X-ray spectroscopy was used to measure the tin content on and within three layers (10 ,m each) beneath the surface. In addition, scanning electron microscopy was conducted. All test preparations significantly reduced tissue loss. Deposition of tin on surfaces was higher without erosion than with erosion, but no incorporation of tin into enamel was found without demineralization. Under erosive conditions, both highly concentrated solutions led to the incorporation of tin up to a depth of 20 ,m; the less-concentrated solution led to small amounts of tin in the outer 10 ,m. The efficacy of tin-containing solutions seems to depend mainly on the incorporation of tin into enamel. [source] Bottom-Up Engineering of Subnanometer Copper Diffusion Barriers Using NH2 -Derived Self-Assembled MonolayersADVANCED FUNCTIONAL MATERIALS, Issue 7 2010Arantxa Maestre Caro Abstract A 3-aminopropyltrimethoxysilane-derived self-assembled monolayer (NH2SAM) is investigated as a barrier against copper diffusion for application in back-end-of-line (BEOL) technology. The essential characteristics studied include thermal stability to BEOL processing, inhibition of copper diffusion, and adhesion to both the underlying SiO2 dielectric substrate and the Cu over-layer. Time-of-flight secondary ion mass spectrometry and X-ray spectroscopy (XPS) analysis reveal that the copper over-layer closes at 1,2-nm thickness, comparable with the 1.3-nm closure of state-of-the-art Ta/TaN Cu diffusion barriers. That the NH2SAM remains intact upon Cu deposition and subsequent annealing is unambiguously revealed by energy-filtered transmission electron microscopy supported by XPS. The SAM forms a well-defined carbon-rich interface with the Cu over-layer and electron energy loss spectroscopy shows no evidence of Cu penetration into the SAM. Interestingly, the adhesion of the Cu/NH2SAM/SiO2 system increases with annealing temperature up to 7.2,J m,2 at 400,°C, comparable to Ta/TaN (7.5,J m,2 at room temperature). The corresponding fracture analysis shows that when failure does occur it is located at the Cu/SAM interface. Overall, these results demonstrate that NH2SAM is a suitable candidate for subnanometer-scale diffusion barrier application in a selective coating for copper advanced interconnects. [source] Catalyst-Free Synthesis and Characterization of Metastable Boron Carbide NanowiresADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Aruna Velamakanni Abstract Catalyst-free growth of boron carbide nanowires is achieved by pyrolysis of diborane and methane at 650,750,°C and around 500 mTorr in a quartz tube furnace. Electron-diffraction analysis using a novel diffraction-scanning transmission electron microscopy (D-STEM) technique indicates that the crystalline nanowires are single-crystal orthorhombic boron carbide. TEM images show that the nanowires are covered by a 1,3,nm thick amorphous layer of carbon. Elemental analysis by electron energy loss spectroscopy (EELS) shows only boron and carbon while energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) show the presence of oxygen as well as boron and carbon. [source] Capacity Fading Mechanism in All Solid-State Lithium Polymer Secondary Batteries Using PEG-Borate/Aluminate Ester as Plasticizer for Polymer ElectrolytesADVANCED FUNCTIONAL MATERIALS, Issue 6 2009Fuminari Kaneko Abstract Solid-state lithium polymer secondary batteries (LPB) are fabricated with a two-electrode-type cell construction of Li|solid-state polymer electrolyte (SPE)|LiFePO4. Plasticizers of poly(ethylene glycol) (PEG)-borate ester (B-PEG) or PEG-aluminate ester (Al-PEG) are added into lithium-conducting SPEs in order to enhance their ionic conductivity, and lithium bis-trifluoromethansulfonimide (LiTFSI) is used as the lithium salt. An improvement of the electrochemical properties is observed upon addition of the plasticizers at an operation temperature of 60,°C. However, a decrease of discharge capacities abruptly follows after tens of stable cycles. To understand the origin of the capacity fading, electrochemical impedance techniques, ex-situ NMR and scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDS) techniques are adopted. Alternating current (AC) impedance measurements indicate that the decrease of capacity retention in the LPB is related to a severe increase of the interfacial resistance between the SPE and cathode. In addition, the bulk resistance of the SPE film is observed to accompany the capacity decay. Ex situ NMR studies combined with AC impedance measurements reveal a decrease of Li salt concentration in the SPE film after cycling. Ex situ SEM/EDS observations show an increase of concentration of anions on the electrode surface after cycling. Accordingly, the anions may decompose on the cathode surface, which leads to a reduction of the cycle life of the LPB. The present study suggests that a choice of Li salt and an increase of transference number is crucial for the realization of lithium polymer batteries. [source] Hydrogen-Assisted Thermal Evaporation Synthesis of ZnS Nanoribbons on a Large Scale,ADVANCED MATERIALS, Issue 4 2003Y. Jiang Semiconductor nanoribbons of ZnS have been synthesized on a large scale via hydrogen-assisted thermal evaporation. The product is characterized by means of electron microscopy and energy-dispersive X-ray spectroscopy, which show that the as-prepared ZnS nanoribbons are single crystals with uniform morphology. A stable and strong emission band centered at 534.5 nm is also associated with the nanoribbons. [source] Deposition of PtxRu1,x Catalysts for Methanol Oxidation in Micro Direct Methanol Fuel CellsISRAEL JOURNAL OF CHEMISTRY, Issue 3-4 2008William E. Mustain Platinum-ruthenium electrodes (PtxRu1-x) have been prepared by electrochemical and electroless deposition and investigated as catalysts for the oxidation of methanol in acidic solutions. PtxRu1-x deposits were electrochemically deposited from acidic chloride electrolytes at potentials between ,0.46 and 0.34 V (vs. NHE). The composition of the electrodeposit was estimated by energy dispersive X-ray spectroscopy and is a strong function of the electrode potential. An empirical model for the deposition process is presented and kinetic parameters are estimated and discussed. Also, the methanol oxidation activity of the PtxRu1-x catalysts was characterized by cyclic voltammetry in 1.0 M CH3OH, 1.0 M H2SO4 solutions. Electroless PtxRu1-x samples were prepared in a modified Leaman bath with hydrazine dihydrochloride as the reducing agent. The kinetic results for the electrochemical deposition of PtxRu1-x were directly applied and the deposition potential was estimated as approximately 0.40 V. [source] Properties of amylopectin/montmorillonite composite films containing a coupling agentJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007D. Nordqvist Abstract The addition of clay to polymers has the combined effects of enhancing both the strength/stiffness and the barrier properties. This investigation presents a novel approach to further enhance the strength/stiffness of cast plasticized amylopectin (AP)/Na+ -montmorillonite clay films using a water-soluble coupling agent, poly[(isobutylene- alt -maleic acid, ammonium salt)- co -(isobutylene- alt -maleic anhydride)], between the filler and the matrix. The addition of clay increased the strength and stiffness of the film and the addition of 0.4 parts of a coupling agent per 1 part clay further increased these properties. The trends were the same after each treatment, and there were always significant differences in stiffness and strength between the films without clay and with clay with 0.4 parts of the coupling agent. The increase in stiffness/strength in the presence of a small amount of the coupling agent suggested that it had a bridging effect, presumably through strong secondary bonds to the clay and to the matrix. Infrared spectroscopy and moisture swelling experiments indicated that ester bonds were formed between the coupling agent and AP. X-ray spectroscopy and transmission electron microscopy revealed that the clay-particle/polymer structure was qualitatively independent of the presence of the coupling agent showing a mixture of intercalated clay stacks and exfoliated platelets. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4160,4167, 2007 [source] Composite coating of bonelike apatite particles and collagen fibers on poly L-lactic acid formed through an accelerated biomimetic coprecipitation processJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2006Yun Chen Abstract Collagen and apatite were coprecipitated as a composite coating on poly L-lactic acid (PLLA) in an accelerated biomimetic process. The incubation solution contained collagen (1 g/L) and simulated body fluid with 5 times inorganic ionic concentrations as human blood plasma. The coating formed on PLLA films and scaffolds after a 24-h incubation was characterized by using energy-dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy (SEM). It was shown that the coating contained carbonated bonelike apatite and collagen, which was similar in composition to natural bone. SEM showed a complex composite coating of submicron bonelike apatite particulates combined with collagen fibrils. It is expected that such biocomposite coating may better facilitate cell interaction and osteoconductivity. This work provided an efficient process to obtain bonelike apatite/collagen composite coating, which is potentially useful in bone tissue engineering. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [source] Reducing ammonia emission from poultry manure composting via struvite formationJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2007Wenxiu Zhang Abstract Composting can provide a viable alternative for poultry manure management in the Fraser Valley of British Columbia, Canada. However, it has a high potential for ammonia emission because of the high nitrogen content of poultry litter. The objective of this study was to reduce ammonia emission by precipitating ammonia into struvite before it can volatilize from the composting matrix. Nitrogen transformation occurs during composting, but struvite formation can help to conserve nitrogen, and does not allow a large amount of nitrogen to be released into the environment as ammonia or nitrate, because ammonium-nitrogen becomes bound in struvite. It would also be possible to remove phosphorus from the manure. A laboratory-scale experiment was conducted to examine the feasibility of struvite formation during poultry manure composting. Magnesium and phosphate salts were supplemented to create favorable conditions to form struvite. Results indicated that ammonia emission was reduced by 40% to 84%, while the nitrogen retention in compost was enhanced. The struvite formed in compost was confirmed by means of X-ray diffraction; and scanning electron microscopy with energy dispersive X-ray spectroscopy. Copyright © 2007 Society of Chemical Industry [source] Evaluation of municipal compost/limestone/iron mixtures as filling material for permeable reactive barriers for in-situ acid mine drainage treatmentJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2003Oriol Gibert Abstract The aim of the present study was to assess the potential of municipal compost as a carbon source for sulfate-reducing bacteria for acid mine drainage bioremediation for use in permeable reactive barriers at high flow rates (>0.1 m d,1). Two different mixtures of municipal compost, limestone and zero-valent iron were assessed in two column experiments. The effluent solution was systematically analysed throughout the experiments. At the end of the experiments precipitates from both columns were withdrawn for scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffractometry examination and solid digestion and sequential extraction were carried out. Results showed that the effluent was free of metals and acidity. It seems that metal removal was not due to biogenic sulfide generation but to pH increase, ie metal (oxy)hydroxides precipitation. These precipitates can sorb other metals onto the surface. Sorption to organic matter could also contribute to metal removal. When zero-valent iron was present, cementation of copper also occurred. It can be concluded that municipal compost was a poor carbon source to support continuous bacterial activity under high flow rates. Copyright © 2003 Society of Chemical Industry [source] Semiautomatic sequence-specific assignment of proteins based on the tertiary structure,The program st2nmrJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 3 2002Primo, Pristov Abstract The sequence-specific assignment of resonances is still the most time-consuming procedure that is necessary as the first step in high-resolution NMR studies of proteins. In many cases a reliable three-dimensional (3D) structure of the protein is available, for example, from X-ray spectroscopy or homology modeling. Here we introduce the st2nmr program that uses the 3D structure and Nuclear Overhauser Effect spectroscopy (NOESY) peak list(s) to evaluate and optimize trial sequence-specific assignments of spin systems derived from correlation spectra to residues of the protein. A distance-dependent target function that scores trial assignments based on the presence of expected NOESY crosspeaks is optimized in a Monte Carlo fashion. The performance of the program st2nmr is tested on real NMR data of an ,-helical (cytochrome c) and ,-sheet (lipocalin) protein using homology models and/or X-ray structures; it succeeded in completely reproducing the correct sequence-specific assignments in most cases using 2D and/or 15N/13C Nuclear Overhauser Effect (NOE) data. Additionally to amino acid residues the program can also handle ligands that are bound to the protein, such as heme, and can be used as a complementary tool to fully automated assignment procedures. © 2002 Wiley Periodicals, Inc. J Comput Chem 23: 335,340, 2002 [source] Hybrid ZnAl-LDH/CNTs nanocomposites: Noncovalent assembly and enhanced photodegradation performanceAICHE JOURNAL, Issue 3 2010Hui Wang Abstract In this article, we reported a facile and effective strategy for assembling hybrid ZnAl-layered double hydroxide/carbon nanotubes (ZnAl-LDH/CNTs) nanocomposites through noncovalent bonds, for the first time, in the presence of L -cysteine molecules. The materials have been characterized by powder X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), thermogravimetry and differential scanning calorimetry (TG-DSC), X-ray photoelectron spectra (XPS) and specific surface area measurement. The results indicate that L -cysteine as bridging linker plays a key role for enhancing both adhesion and dispersion of LDH nanocrystallites onto the surface of CNTs matrix through the interfacial interaction, and effectively inhibits the in situ growth of LDH crystallites, thus resulting in remarkably reduced LDH crystallite sizes; the Eu(III) fluorescence quenching in intercalated-Eu(III)complex LDH/CNTs nanocomposite can occur because of the interaction between LDH crystallites and CNTs matrix. Furthermore, it is found that as-assembled hybrid LDH/CNTs nanocomposites exhibit excellent performance for photodegradation of methyl orange molecules under UV irradiation, which is closely related to the unique hybrid nanostructure and composition of composites. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] The effect of an Ni,Cr protective layer on cyclic oxidation of Ti3AlJOURNAL OF MICROSCOPY, Issue 1 2006I. CVIJOVI Summary The effect of an 80Ni,20Cr (at.%) metallic coating on the cyclic oxidation behaviour of a Ti3Al-based alloy with the composition Ti,25Al,11Nb (at.%) was investigated in this study. Cyclic oxidation tests were carried out in air at 600 °C and 900 °C for 120 h. For one cycle test, the specimens were held for 24 h at test temperature and then furnace-cooled to room temperature. The oxidation rate was determined by plotting the mass gain per unit surface area of the specimen vs. exposure time. The morphology and composition of the oxidation products were characterized on the cross-section of the specimens by scanning electron microscopy, energy-dispersive X-ray spectroscopy and atomic force microscopy. The oxidation scale forms during exposure at both 600 °C and 900 °C. TiO2 is the main oxide component, whereas the Al2O3 layer appears only discontinuously. The remarkable improvement in oxidation resistance at 900 °C was attributed to the chemical composition and structure of the scale formed on the 80Ni,20Cr coating. [source] Streaming potential characterization of LBL membranes on porous ceramic supportsAICHE JOURNAL, Issue 4 2007Yiwei Chen Abstract An in-situ characterization of the growth of the self-assembled polyelectrolyte membranes on the porous support was conducted by applying transmembrane streaming potential measurement via surface charge monitoring. The membranes were prepared by layer-by-layer alternative deposition of poly (allylamine hydrochloride) and poly (styrenesulfonate) on porous ceramic supports. The surface charge variations of membranes as functions of different top-assembled materials and numbers of deposited cycles were investigated. Different top-assembled materials make isoelectric points of the as-prepared membranes drift in opposite directions and also lead to symmetrical signal changes of zeta-potential in salt solutions at the isoelectric points of the supports. Ex-situ characterizations, including scanning electron microscopy, atomic force microscopy, and energy dispersive X-ray spectroscopy, also confirm the alternative deposition of polyelectrolytes. It is demonstrated that the transmembrane streaming potential measurement is effective in studying the growth of layer-by-layer membranes on porous support. © 2007 American Institute of Chemical Engineers AIChE J, 2007 [source] Preparation, characterisation and modification of carbon-based monolithic rods for chromatographic applicationsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9 2010Ali H. Eltmimi Abstract A range of porous carbon-based monolithic (PCM) rods with flow-through pore sizes of 1, 2, 5 and 10,,m, were produced using a silica particle template method. The rods were characterised using SEM and energy-dispersive X-ray spectroscopy, BET surface area and porous structure analysis, dilatometry and thermal gravimetry. SEM evaluation of the carbon monolithic structures revealed an interconnected rigid bimodal porous structure and energy-dispersive X-ray spectroscopy analysis verified the quantitative removal of the embedded silica beads. The specific surface areas of the 1, 2, 5 and 10,,m rods were 178, 154, 84 and 125,m2/g after pyrolysis and silica removal, respectively. Shrinkage of the monolithic rods during pyrolysis is proportional to the particle size of the silica used and ranged from 9 to 12%. Mercury porosimetry showed a narrow distribution of pore sizes, with an average of ,700,nm for the 1,,m carbon monolith. The suitability of bare and surface oxidised PCM rods for the use as a stationary phase for reversed and normal phase LC was explored. The additional modification of PCM rods with gold micro-particles followed by 6-mercaptohexanoic acid was performed and ion-exchange properties were evaluated. [source] Radiation damage in protein crystals examined under various conditions by different methodsJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2009Elspeth F. Garman Investigation of radiation damage in protein crystals has progressed in several directions over the past couple of years. There have been improvements in the basic procedures such as calibration of the incident X-ray intensity and calculation of the dose likely to be deposited in a crystal of known size and composition with this intensity. There has been increased emphasis on using additional techniques such as optical, Raman or X-ray spectroscopy to complement X-ray diffraction. Apparent discrepancies between the results of different techniques can be explained by the fact that they are sensitive to different length scales or to changes in the electronic state rather than to movement of atoms. Investigations have been carried out at room temperature as well as cryo-temperatures and, in both cases, with the introduction of potential scavenger molecules. These and other studies are leading to an overall description of the changes which can occur when a protein crystal is irradiated with X-rays at both cryo- and room temperatures. Results from crystallographic and spectroscopic radiation-damage experiments can be reconciled with other studies in the field of radiation physics and chemistry. [source] Silicon drift and pixel devices for X-ray imaging and spectroscopyJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2006G. Lutz Starting from the basic photon detection process in semiconductors, the function, principles and properties of sophisticated silicon detectors are discussed. These detectors are based on, or inspired by, the semiconductor drift detector. They have already shown their potential in X-ray astronomy (pn-CCD) and in X-ray spectroscopy (silicon drift diode), and further detector types (DEPFET pixel detector and macro-pixel detector) are under development for several other future experiments. The detectors seem to be very well suited for synchrotron radiation experiments. [source] Synchrotron techniques for metalloproteins and human disease in post genome eraJOURNAL OF SYNCHROTRON RADIATION, Issue 1 2004S. Samar Hasnain Metalloproteins make up some 30% of proteins in known genomes. Metalloproteins are a special class of proteins that utilise the unique properties of metal atoms in conjunction with the macromolecular assembly to perform life-sustaining processes. A number of metalloproteins are known to be involved in many disease states including ageing processes. The incorporation of the metal ion is a very tightly regulated process that, in vivo, very often requires specific chaperons to deliver and help incorporate the metal atom in the macromolecule. The lack of or inappropriate incorporation of metals along with genetic factors can lead to the mis-function of these proteins leading to disease. The mis-functions due to genetic alterations that lead to diseases like ALS (amyotrophic lateral sclerosis or motor neuron disease) and Creutzfeld Jacob disease (CJD) are now well recognised. Synchrotron radiation sources provide a unique set of structural tools, which in combination can prove extremely powerful in providing a comprehensive picture of these complex biological systems. In particular for metalloproteins, the combined use of X-ray crystallography, X-ray solution scattering and X-ray spectroscopy (XAFS) is extremely useful. We are currently engaged in a structural study where our aim is to characterize structurally and functionally metalloproteins and then transfer this knowledge to afford the problem of the mis-function of metalloproteins that lead to these terminal illnesses, either due to a gain of function/property or a loss of function/property. In this context, the benefits of adopting the `philosophy' being developed for the structural genomics effort are highlighted. [source] Deposition of Carbonated Hydroxyapatite (CO3HAp) on Poly(Methylmethacrylate) Surfaces by Decomposition of Calcium,EDTA ChelateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2008Yusuf Yusufoglu Inspired from the nature, the development of organic,inorganic composites between polymers and hydroxyapatite (HAp) has been investigated extensively. In this study, bone-like apatite (carbonated hydroxyapatite, CO3HAp) was precipitated on poly(methylmethacrylate) (PMMA) films by the oxidative decomposition of Ca,EDTA (calcium,ethylenediamine tetraacetate) chelates. Corona-treated PMMA films were soaked in a Ca,EDTA,PO4,H2O2 solution and aged at 63°C and pH,9 for times ranging from 1 to 24 h. Apatite formed on PMMA films was characterized by X-ray diffraction, Fourier transform infrared (FTIR), Scanning electron microscope, energy-dipersive X-ray spectroscopy, and carbon analysis. The apatite was found to be CO3HAp with Ca/P atomic ratio ranging between 1.3 and 1.9. Elemental analyses indicated that the carbonate content of the apatite phase was around 6.5 wt% after 24 h of aging time. Lattice parameters were estimated using a Rietveld profile-analysis and found to be a=0.9438 nm and c=0.6901 nm. Furthermore, FTIR spectra indicated that the apatite deposited on PMMA was B-type CO3HAp, in which carbonate ions occupy the phosphate sites. In the first 3 h of aging, isolated rod-like HAp particles were observed. With time, the needle-like crystallites radiate from a nucleus to form double-spherulite shape particles. The crystallites grew into a continuous layer with a thickness of ,15 ,m after 24-h aging. The adhesive strength between the PMMA substrate and the apatite layer was determined to be around 1.7 MPa. [source] Hydrothermal Synthesis YbMnO3 and LuMnO3 PlateletsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2008Gangqiang Zhu Single-crystalline YbMnO3 and LuMnO3 platelets have been successfully synthesized via a simple hydrothermal process at 250°C for 24 h. X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and selected area electron diffraction patterns were used to characterize the as-synthesized samples. The result reveals that both of the as-synthesized YbMnO3 and LuMnO3 are of hexagonal phase. The effect of treatment time on the phase of the final products has been studied, and a possible formation mechanism of YbMnO3 and LuMnO3 is proposed. [source] Microstructure of Nanocrystalline Yttria-Doped Zirconia Thin Films Obtained by Sol,Gel ProcessingJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2008Benjamin Butz Nano- and microcrystalline yttria-stabilized zirconia (YSZ) thin films with a dopant concentration of 8.3±0.3 mol% Y2O3 were prepared with a variation in grain size by two orders of magnitude. A sol,gel-based method with consecutive rapid thermal annealing was applied to fabricate YSZ films, resulting in about 400 nm YSZ on sapphire substrates. The average grain sizes were varied between 5 nm and 0.5 ,m by heat treatment in the temperature range of 650°,1350°C for 24 h. High-resolution (HRTEM) and conventional transmission electron microscopy analyses confirmed specimens,irrespective of the thermal treatment,consisting of cubic (c -)ZrO2 grains with nanoscaled tetragonal precipitates coherently embedded in the cubic matrix. Energy-dispersive X-ray spectroscopy and HRTEM on a large number of specimens yielded a homogeneous yttria concentration within the grains and at the grain boundaries with the absence of impurities, i.e. silica at the grain boundaries. [source] Effect of pH on the Carbonate Incorporation into the Hydroxyapatite Prepared by an Oxidative Decomposition of Calcium,EDTA ChelateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2008Yusuf Yusufoglu In this study, the carbonate incorporation into the hydroxyapatite (HAp) lattice under various pH conditions was investigated. Crystalline-sodium and carbonate-containing calcium HAp (NaCO3HAp) powders were prepared using an oxidative decomposition of calcium,EDTA chelates in a sodium phosphate solution with hydrogen peroxide. The powders obtained were characterized by X-ray diffraction, infrared spectroscopy, thermal gravimetric analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and elemental analysis. Depending on pH, spherical particles approximately 3.5 ,m in diameter or hexagonal prismatic particles measuring 3,9 ,m in length were obtained. Various characterization techniques showed that the precipitates were a single-phase NaCO3HAp. The carbonate content and the lattice parameters of the HAp were a function of solution pH. Maximum carbonate incorporated into the HAp lattice was at pH=10, corresponding to lattice parameters of a=0.93880 nm and c=0.69070 nm. Furthermore, spectroscopic analyses indicate that the as-prepared samples are B-type carbonated HAp, in which carbonate ions occupy the phosphate sites. After heat treatment at 965°C, most of the carbonate is removed from the HAp lattice. [source] | ||||||||||||||||||||||||||||||||||