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91.
First-principles molecular dynamics has been used to investigate the structural, vibrational, and energetic properties of formic acid, formic acid-formate anion dimers, and liquid formic acid in a periodically repeated box with 32 formic acid molecules. We found that in liquid formic acid the hydrogen-bonded clusters mainly consist of linear branching chains. From our simulation, we got good agreement with the available structural and dynamical data. We also studied the proton transfer in the cis-formic acid-formate anion dimer, and we showed that this proton transfer does not have any potential barrier. The hydrogen bonding statistics as well as the mean lifetime of the hydrogen bonds are analyzed. 相似文献
92.
Peter Wilhartitz R. Krismer H. Hutter M. Grasserbauer S. Weinbruch H. M. Ortner 《Fresenius' Journal of Analytical Chemistry》1995,353(5-8):524-532
Applying a recently developed three dimensional SIMS imaging technique major differences in the distribution of trace elements in ultra high purity Mo and W have been found. In the electron beam melted material severe grain boundary segregation of trace elements have occurred whereas in the hot pressed material trace elements have been present as precipitates with a size of 5–15 m. Guided by the results of the 3D-SIMS images and the advantages of the sintering process a material with homogeneous distribution of trace elements has been developed and characterised. To test the applicability for the microelectronics industry, sputtering targets have been manufactured out of this new material and layers with a thickness of 350 nm have been sputterdeposited on silicon. The quality of these layers, with respect to particle emission and the distribution of trace elements, was evaluated by EPMA and 3D-SIMS imaging. Further improvement of the sintering process led to a material with a completely homogeneous distribution of C, H, N, O and S to minimise the outgassing and diffusion of impurities.Abbreviations BSE
Back scattered electron
- EPMA
Electron probe micro analysis
- GAAS
Graphite furnace atomic absorption spectrometry
- GDMS
Glow discharge mass spectrometry
- ICP-AES
Inductively coupled plasma atomic emission spectrometry
- ICP-MS
Inductively coupled plasma mass spectrometry
- SIMS
Secondary ion mass spectrometry
- ULSI
Ultra large scale integration 相似文献
93.
In the present study an evolution equation for the Cauchy stress tensor is proposed for an isotropic elasto-visco-plastic
continuum. The proposed stress model takes effects of elasticity, viscosity and plasticity of the material simultaneously
into account. It is ascribed with some scalar coefficient functions and, in particular, with an unspecified tensor-valued
function N, which is handled as an independent constitutive quantity. It is demonstrated that by varying the values and the specific
functional forms of these coefficients and N, different known models in non-Newtonian rheology can be reproduced. A thermodynamic analysis, based on the Müller–Liu entropy
principle, is performed. The results show that these coefficients and N are not allowed to vary arbitrarily, but should satisfy certain restrictions. Simple postulates are made to further simplify
the deduced general results of the thermodynamic analysis. They yield justification and thermodynamic consistency of the existing
models for a class of materials embracing thermoelasticity, hypoelasticity and in particular hypoplasticity, of which the
thermodynamic foundation is established successively for the first time in literature. The study points at the wide applicability
and practical usefulness of the present model in different fields from non-Newtonian fluid to solid mechanics. In this paper
the thermodynamic analysis of the proposed evolution-type stress model is discussed, its applications are reported later.
相似文献
94.
Significant Substituent Effect on the Anomerization of Pyranosides: Mechanism of Anomerization and Synthesis of a 1,2‐cis Glucosamine Oligomer from the 1,2‐trans Anomer 下载免费PDF全文
Dr. Shino Manabe Prof. Hiroko Satoh Prof. Jürg Hutter Dr. Hans Peter Lüthi Dr. Teodoro Laino Dr. Yukishige Ito 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(1):124-132
Aminoglycosides containing a 2,3‐trans carbamate group easily undergo anomerization from the 1,2‐trans glycoside to the 1,2‐cis isomer under mild acidic conditions. The N‐substituent of the carbamate has a significant effect on the anomerization reaction; in particular, an N‐acetyl group facilitated rapid and complete α‐anomerization. The differences in reactivity due to the various N‐substituents were supported by the results of DFT calculations; the orientation of the acetyl carbonyl group close to the anomeric position was found to contribute significantly to the directing of the anomerization reaction. By exploiting this reaction, oligoaminoglycosides with multiple 1,2‐cis glycosidic bonds were generated from 1,2‐trans glycosides in a one‐step process. 相似文献
95.
Matthew J. Coady Nuwansiri N. K. Getangama Aria Khalili Michael Wood Kent E. Nielsen John R. de Bruyn Jeffrey L. Hutter Robert J. Klassen Anne-Marie Kietzig Paul J. Ragogna 《Journal of polymer science. Part A, Polymer chemistry》2020,58(7):1022-1029
Preventing ice growth on infrastructure, vehicles, and appliances remains a significant engineering challenge. Damage caused by ice growth on these installations can be expensive to repair, and their failure can be dangerous. Materials such as cross-linked polymer networks make effective anti-ice coatings and can prevent ice growth: reducing the cost of infrastructure repairs and limiting downtime. A link between cross-link density and ice adhesion has been demonstrated, such that lower cross-link density materials tend toward lower ice adhesion. Here we describe a method of lowering cross-link density by incorporating the covalently bound comonomers methyl methacrylate, lauryl methacrylate, and styrene into UV-cured PDMS-based polymer networks. Cross-link density, hardness, surface roughness, and ice adhesion on these materials are tested, showing the influence of comonomer proportions on their properties. Durability is found to increase with the addition of 5, 10, and 25 wt% comonomer, with little to no effect on ice adhesion until 25 wt%, where increases in ice adhesion are observed. Coatings show promisingly low ice adhesion of ~50 kPa, maintaining this low adhesion for up to 50 deicing cycles. 相似文献
96.
97.
Sabine Dreer Peter Wilhartitz Kurt Piplits Herbert Hutter Michael Kopnarski Gernot Friedbacher 《Mikrochimica acta》2000,133(1-4):75-87
Silicon- and aluminium oxynitride films have gained attention because of their interesting properties in various fields of
technology. The specific properties strongly depend on the concentration of oxygen and nitrogen in the films. For the quantitative
analysis of homogeneous silicon- and aluminium oxynitride films, EPMA has been proven a very reliable and precise method of
analysis. In order to characterise films with graded composition or interface effects between the film and the substrate it
is necessary to use sputter depth profiling techniques such as SIMS, hf-SNMS, AES, or hf-GD-OES. Unfortunately, stoichiometric
silicon- and aluminium oxynitride films are insulating and therefore charge compensation has to be applied.
For the quantification it was necessary to prepare calibration samples which have been analysed by different bulk analytical
techniques such as NRA, RBS and EPMA. With these calibration samples, sensitivity factors have been determined and the functional
dependence of the sensitivity factors on the composition has been derived. The advantages and disadvantages of the different
sputtering techniques and the applicability of the obtained sensitivity functions for the quantitative depth profiling of
silicon- and aluminium oxynitride films are discussed. 相似文献
98.
F. dell'Isola M. Guarascio K. Hutter 《Archive of Applied Mechanics (Ingenieur Archiv)》2000,70(5):323-337
Summary The principle of virtual power is used to derive the equilibrium field equations of a porous solid saturated with a fluid,
including second density-gradient effects; the intention is the elucidation and extension of the effective stress principle
of Terzaghi and Fillunger. In the context of a first density-gradient theory for a saturated solid we interpret the porewater
pressure as a Lagrange multiplier in the expression for the deformation energy, assuring that the saturation constraint is
verified. We prove that this saturation pressure is distributed among the constituents according to their respective volume
fraction (Delesse law) only if they are both true density-preserving. We generalize the Delesse law to the case of compressible
constituents. If a material-dependent effective stress contribution is to arise, it is, in general, nonvanishing simultaneously
in both the solid and fluid constituents. Moreover, saturation pressure, effective stresses and compressibility constitutive
equations determine the exchange volume forces. In a theoretical formulation without non-isotropic strain measures, second
density-gradient effects must be incorporated, not only to accommodate for the equilibrium-solid-shear stress and the interaction
among neighboring solid-matrix pores, but also to describe internal capillarity effects. The earlier are accounted for by
a dependence of the thermodynamic energy upon the density-gradient of the solid, while the latter derives from a mixed density-gradient
dependence. Examples illustrate the necessity of these higher gradient effects for properly posed boundary value problems
describing the mechanical behaviour of the disturbed rock zone surrounding salt caverns. In particular, we show that solid
second-gradient strains allow for the definition of the concept of static permeability, which is distinct from the dynamic
Darcy permeability.
Received 1 February 1999; accepted for publication 9 March 1999 相似文献
99.
Johannes Schnöller Ernst Pittenauer Herbert Hutter Günter Allmaier 《Journal of mass spectrometry : JMS》2009,44(12):1724-1732
Commercial copper wire and its polymer insulation cladding was investigated for the presence of three synthetic antioxidants (ADK STAB AO412S, Irganox 1010 and Irganox MD 1024) by three different mass spectrometric techniques including electrospray ionization–ion trap–mass spectrometry (ESI–IT–MS), matrix‐assisted laser desorption/ionization reflectron time‐of‐flight (TOF) mass spectrometry (MALDI–RTOF–MS) and reflectron TOF secondary ion mass spectrometry (RTOF–SIMS). The samples were analyzed either directly without any treatment (RTOF–SIMS) or after a simple liquid/liquid extraction step (ESI–IT–MS, MALDI–RTOF–MS and RTOF–SIMS). Direct analysis of the copper wire itself or of the insulation cladding by RTOF–SIMS allowed the detection of at least two of the three antioxidants but at rather low sensitivity as molecular radical cations and with fairly strong fragmentation (due to the highly energetic ion beam of the primary ion gun). ESI–IT‐ and MALDI–RTOF–MS‐generated abundant protonated and/or cationized molecules (ammoniated or sodiated) from the liquid/liquid extract. Only ESI–IT–MS allowed simultaneous detection of all three analytes in the extract of insulation claddings. The latter two so‐called ‘soft’ desorption/ionization techniques exhibited intense fragmentation only by applying low‐energy collision‐induced dissociation (CID) tandem MS on a multistage ion trap‐instrument and high‐energy CID on a tandem TOF‐instrument (TOF/RTOF), respectively. Strong differences in the fragmentation behavior of the three analytes could be observed between the different CID spectra obtained from either the IT‐instrument (collision energy in the very low eV range) or the TOF/RTOF‐instrument (collision energy 20 keV), but both delivered important structural information. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
100.
Murdachaew G Mundy CJ Schenter GK Laino T Hutter J 《The journal of physical chemistry. A》2011,115(23):6046-6053
We have applied an efficient electronic structure approach, the semiempirical self-consistent polarization neglect of diatomic differential overlap (SCP-NDDO) method, previously parametrized to reproduce properties of water clusters by Chang, Schenter, and Garrett [ J. Chem. Phys. 2008 , 128 , 164111 ] and now implemented in the CP2K package, to model ambient liquid water at 300 K (both the bulk and the liquid-vapor interface) and cubic ice at 15 and 250 K. The SCP-NDDO potential retains its transferability and good performance across the full range of conditions encountered in the clusters and the bulk phases of water. In particular, we obtain good results for the density, radial distribution functions, enthalpy of vaporization, self-diffusion coefficient, molecular dipole moment distribution, and hydrogen bond populations, in comparison to experimental measurements. 相似文献