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61.
Guhados G Wan W Hutter JL 《Langmuir : the ACS journal of surfaces and colloids》2005,21(14):6642-6646
The ability of the atomic force microscope to measure forces with subnanonewton sensitivity at nanometer-scale lateral resolutions has led to its use in the mechanical characterization of nanomaterials. Recent studies have shown that the atomic force microscope can be used to measure the elastic moduli of suspended fibers by performing a nanoscale three-point bending test, in which the center of the fiber is deflected by a known force. We extend this technique by modeling the deflection measured at several points along a suspended fiber, allowing us to obtain more accurate data, as well as to justify the mechanical model used. As a demonstration, we have measured a value of 78 +/- 17 GPa for Young's modulus of bacterial cellulose fibers with diameters ranging from 35 to 90 nm. This value is considerably higher than previous estimates, obtained by less direct means, of the mechanical strength of individual cellulose fibers. 相似文献
62.
Christian Brunner Herbert Hutter Peter Wilhartitz Manfred Grasserbauer 《Mikrochimica acta》1997,125(1-4):69-72
Spallation of the protective oxide layer formed during hot gas oxidation is the main reason for the corrosion of high purity powder metallurgically produced chromium[1]. To explain the formation and occasional spallation of the oxide layer a chromium sample subjected to two consecutive oxidation processes in16O and18O atmosphere at high temperature was characterised by 2D and 3D SIMS.The formation of the protective oxide can be described by the diffusion of chromium from the bulk to the surface and the reaction of the chromium atoms with the oxygen from the gaseous phase. The very low solubility of nitrogen in chromium oxide indicates its inability to diffuse through the growing oxide layer and explains the enrichment of nitrogen (same mechanism applies for chlorine) in the interface metal/oxide. The accumulation of trace elements within the interface during the oxidation process explains the reduced adhesion power of the passivation layer and its spallation.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday 相似文献
63.
Katharina Gammer Erhard Ogris Peter J. Uggowitzer Herbert Hutter 《Mikrochimica acta》2003,141(1-2):23-27
Strontium modified aluminium–silicon cast alloys are well known for their outstanding mechanical properties as they combine
excellent strength with good ductility that is due to a modification of brittle Si in the eutectic with traces of Sr (0.3–0.5 wt%).
Although the level of Sr addition is very low, formation of ternary AlSiSr phases with deleterious effects on the ductility
can take place. Consequently, there is a certain need of alternative modifying elements. Following the theory of Lu and Hellawell
which predicts an optimal atomic size for good modification, Eu, which has an atomic radius close to that optimal size, was
additionally used as a modifying element. This study presents SIMS (secondary ion mass spectrometer) investigations of the
3D-distributions of the main alloying and trace elements in Al–Si feedstock alloys for thixocasting modified with Sr and Eu,
respectively.
Received October 1, 2001; accepted May 21, 2002 相似文献
64.
Markus Wagner Marius Lindauer Mustafa Mısır Samadhi Nallaperuma Frank Hutter 《Journal of Heuristics》2018,24(3):295-320
Many real-world problems are composed of several interacting components. In order to facilitate research on such interactions, the Traveling Thief Problem (TTP) was created in 2013 as the combination of two well-understood combinatorial optimization problems. With this article, we contribute in four ways. First, we create a comprehensive dataset that comprises the performance data of 21 TTP algorithms on the full original set of 9720 TTP instances. Second, we define 55 characteristics for all TPP instances that can be used to select the best algorithm on a per-instance basis. Third, we use these algorithms and features to construct the first algorithm portfolios for TTP, clearly outperforming the single best algorithm. Finally, we study which algorithms contribute most to this portfolio. 相似文献
65.
The content and the three dimensional distribution of impurities play an important role in the production process of high
purity rhenium powder (99.99% purity grade) and for its further use as alloying and coating agent in high temperature applications.
In this paper the characterization of raw Re granulate, Re powder, cleaned by heat treatment, Re coatings, produced by most
common preparation methods (PVD and VPS) and PM Re by means of SIMS is presented. The analysis of the three dimensional distribution
of trace elements is performed by 3D SIMS. The quantification of carbon, which was not possible with other analytical techniques
as a result of the high volatility of Re2O7 until now, has been carried out by SIMS depth profile analysis. It is discussed if internal standards, produced by introduction
of defined amounts of carbon soot to the Re powder lead to useful results. 相似文献
66.
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
67.
68.
In the final step of secondary metallurgical steel processing, calcium is added. Besides Mg, Ca is the most powerful deoxidiser and desulfurisation agent. It reacts with dissolved oxygen and sulfur and reduces oxides and sulfides thereby forming non-metallic inclusions. Within this paper we present the analysis of such inclusions in a low-carbon chromium-steel. Depending on the time of quenching of the steel sample, different structures were revealed by REM, Auger and SIMS: If the steel was quenched immediately after Ca-addition, non-metallic inclusions that appeared to have "cavities" could be detected with SEM. SIMS investigations of these particles showed ring-shaped structures and revealed that the ring is made up of Al, Ca, Mg, O and S. No secondary ions however could be retrieved from the core inside the ring, thus leaving the nature of the "cavities" unclear. If the steel sample was quenched 3 min after Ca addition, inclusions did not have a ring-shaped structure but a compact one. 相似文献
69.
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
70.