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Atomic Composition (atomic + composition)
Selected AbstractsAb Initio Guided Design of bcc Ternary Mg,Li,X (X,=,Ca, Al, Si, Zn, Cu) Alloys for Ultra-Lightweight ApplicationsADVANCED ENGINEERING MATERIALS, Issue 7 2010William Art Counts Abstract Ab initio calculations are becoming increasingly important for designing new alloys as these calculations can accurately predict basic structural, mechanical, and functional properties using only the atomic composition as a basis. In this paper, fundamental physical properties (like formation energies and elastic constants) of a set of bcc Mg,Li and Mg,Li-based compounds are calculated using density functional theory (DFT). These DFT-determined properties are in turn used to calculate engineering parameters such as (i) specific Young's modulus (Y/,) or (ii) shear over bulk modulus ratio (G/B) differentiating between brittle and ductile behavior. These parameters are then used to identify those alloys that have optimal mechanical properties for lightweight structural applications. First, in case of the binary Mg,Li system, an Ashby map containing Y/, versus G/B shows that it is not possible to increase Y/, without simultaneously increasing G/B (i.e., brittleness) by changing only the composition of a binary alloy. In an attempt to bypass such a fundamental materials-design limitation, a set of Mg,Li,X ternaries (X,=,Ca, Al, Si, Cu, Zn) based on stoichiometric Mg,Li with CsCl structure was studied. It is shown that none of the studied ternary solutes is able to simultaneously improve both specific Young's modulus and ductility. [source] Structure and Mechanical Properties of Polyurethane/Silica Hybrid CoatingsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2005Yongchun Chen Abstract Summary: Polyurethane/silica hybrid coatings were prepared via in situ (IS) or blending (BL) method using different acidic silica sols. The effects of preparation methods, silica types, and content on the structure and mechanical properties of the hybrid coatings were investigated. It was found that there existed two types of silica phases in the hybrid coatings: silica-rich agglomerate and primary silica-rich phase, whose size and compactness depended upon the silica types and the preparation methods. Introducing silica could result in obvious changes in surface free energy, atomic composition, and mechanical properties of the hybrid coatings. Typical SEM image of the fractured surface of hybrids obtained by the in situ method. [source] Carbon Nanotubes Functionalized in Oxygen and Water Low Pressure Discharges used as Reinforcement of Polyurethane CompositesPLASMA PROCESSES AND POLYMERS, Issue S1 2009Lenka Zají, ková Abstract The functionalization of multi-walled CNTs in O2/Ar and H2O/Ar low pressure capacitive discharges was studied by XPS and FT-IR. The pristine and functionalized CNTs were used as fillers in polyurethane paints. Successful plasma functionalization was confirmed by changes in atomic composition and chemical shift of the XPS atomic signals. The functionalization was indicated also by the shift of IR absorption peaks corresponding to the motion of carbon skeleton, especially the peak at about 1,560,cm,1. The presence of carbonyl was confirmed by IR absorption peak at 1,723,cm,1 only for O2/Ar plasma. The plasma functionalized CNTs increased significantly the universal and plastic hardness of the CNTs reinforced polyurethane as compared to the composites with pristine CNTs. [source] On-Line HPLC-UV-mass spectrometry and tandem mass spectrometry for the rapid delineation and characterization of differences in complex mixtures: a case study using toxic oil variantsBIOMEDICAL CHROMATOGRAPHY, Issue 5 2002Frank W. Crow An integrated differential approach to the characterization of complex mixtures is presented which includes the targeting of liquid chromatography (LC) peaks for identification using characteristic UV adsorption of the LC peak, subsequent molecular weight and formula determination using accurate mass LC mass spectrometry (MS), and structure characterization using accurate mass LC-tandem mass spectrometry. The use of differential UV adsorption aids in narrowing the scope of the study to only specific peaks of interest. Accurate mass measurement of the molecular ion species provides molecular weight information as well as atomic composition information. The tandem MS (MS/MS) spectra provide fragmentation information which allows for structural characterization of each component. Accurate mass assignment of each of the fragment ions in the MS/MS spectrum provides atomic composition for each of the fragment ions and thus further aids in the structural characterization. These experiments are facilitated through the use of on-line LC-MS and LC-MS/MS with in-line UV detection. A synthetic toxic oil (STO) related to Toxic Oil Syndrome is studied with a focus on possible contaminants resulting from the interaction of aniline, used as a denaturant, with the normal components of the oil. A differential analysis between the STO and a control oil is performed. LC peaks were targeted using UV absorbance to indicate the possible presence of the aniline moiety. Further differential analysis was performed through the determination of the MS signals associated with each component separated on the LC. Finally, the MS/MS data was also used to determine if the fragmentation of the targeted components indicated the presence of aniline. The MS/MS and accurate mass data were used to assign the structures for the targeted components. Copyright © 2002 John Wiley & Sons, Ltd. [source] Synthesis and Characterization of Tris(,-ketoiminato)ruthenium(III) Complexes: Potential Precursors for CVD of Ru and RuO2 Thin Films,CHEMICAL VAPOR DEPOSITION, Issue 3 2004T.-Y. Chou Abstract The synthesis and characterization of RuIII metal complexes [Ru(keim1)3] (1) and [Ru(keim2)3] (2) are reported, where (keim)H is an abbreviation for the fluorinated ketoimine ligands with formula HOC(CF3)=CHCR=NMe; (keim1)H with R,=,Me and (keim2)H with R,=,CF3. These newly synthesized complexes were characterized by spectroscopic methods, while the second complex, 2, was further examined by single-crystal X-ray diffraction (XRD), revealing an octahedral coordination for the Ru cation, with three ketoiminate arranged in a mer -configuration, a consequence of the enhanced steric interaction between ligands. Moreover, both Ru metal complexes show good volatility and thermal stability. CVD experiments were conducted using these complexes at temperatures of 325,450,°C. The Ru metal and RuO2 thin films on silicon wafers were successfully obtained using either a mixture of 2,% O2 in argon or pure O2 as the carrier gas, respectively. Our result shows that a 2,% O2 concentration induces the formation of Ru metal, while that only complex 1 gives formation of a columnar RuO2 phase upon switching to pure O2 as the CVD carrier gas. Scanning electron microscopy (SEM) images were taken to reveal surface morphologies, while X-ray photoelectron spectroscopy (XPS) and XRD were utilized to access their atomic composition as well as the intrinsic packing of the as-deposited thin film materials. [source] Method for the elucidation of the elemental composition of low molecular mass chemicals using exact masses of product ions and neutral losses: application to environmental chemicals measured by liquid chromatography with hybrid quadrupole/time-of-flight mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2005Shigeru Suzuki A method for elucidating the elemental compositions of low molecular weight chemicals, based primarily on mass measurements made using liquid chromatography (LC) with time-of-flight mass spectrometry (TOFMS) and quadrupole/time-of-flight mass spectrometry (LC/QTOFMS), was developed and tested for 113 chemicals of environmental interest with molecular masses up to ,400,Da. As the algorithm incorporating the method is not affected by differences in the instrument used, or by the ionization method and other ionization conditions, the method is useful not only for LC/TOFMS, but also for all kinds of mass spectra measured with higher accuracy and precision (uncertainties of a few mDa) employing all ionization methods and on-line separation techniques. The method involves calculating candidate compositions for intact ionized molecules (ionized forms of the sample molecule that have lost or gained no more than a proton, i.e., [M+H]+ or [M,H],) as well as for fragment ions and corresponding neutral losses, and eliminating those atomic compositions for the molecules that are inconsistent with the corresponding candidate compositions of fragment ions and neutral losses. Candidate compositions were calculated for the measured masses of the intact ionized molecules and of the fragment ions and corresponding neutral losses, using mass uncertainties of 2 and 5,mDa, respectively. Compositions proposed for the ionized molecule that did not correspond to the sum of the compositions of a candidate fragment ion and its corresponding neutral loss were discarded. One, 2,5, 6,10, 11,20, and >20 candidate compositions were found for 65%, 39%, 1%, 1%, and 0%, respectively, for the 124 ionized molecules formed from the 113 chemicals tested (both positive and negative ions were obtained from 11 of the chemicals). However, no candidate composition was found for 2% of the test cases (i.e., 3 chemicals), for each of which the measured mass of one of the product ions was in error by 5,6.7,mDa. Copyright © 2005 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||