Surface Studies of Polymers with a Well-Defined Segmental Length by ToF-SIMS and XPS. Relationship between the Surface Chemical Composition and Segmental Length

2000 ◽  
Vol 33 (21) ◽  
pp. 8002-8005 ◽  
Author(s):  
Lin Li ◽  
Chi-Ming Chan ◽  
Shiyong Liu ◽  
Lijia An ◽  
Kai-Mo Ng ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Surface Chemical ◽  
Surface Studies ◽  
Surface Chemical Composition ◽  
Tof Sims

scholarly journals Spectra of M Dwarfs - Dimmed by Dust

1998 ◽  
Vol 11 (1) ◽  
pp. 439-440
Author(s):  
T. Tsuji ◽  
K. Ohnaka ◽  
W. Aoki ◽  
H.R.A. Jones
Keyword(s):  
Chemical Composition ◽  
Brown Dwarfs ◽  
Surface Chemical ◽  
Basic Information ◽  
M Dwarfs ◽  
Surface Chemical Composition ◽  
Molecular Lines ◽  
Low Mass

Spectra of M dwarfs are rich in atomic and molecular lines. These spectra provide such basic information as Teff (or radius), log g (or mass), surface chemical composition, and something more (e.g. activity) if properly interpreted. It is recognized, however, that spectra of M dwarfs are already dimmed by the dust formed in their photospheres (Tsuji et al. 1996a) and this effect, which has been overlooked until recently, should be taken into account in any interpretation and analysis of the spectra of very low mass objects (VLMOs) including late M dwarfs and brown dwarfs.

scholarly journals Surface Texture of Microcrystalline Tunnel-Structured Manganese(IV) Oxides: Nitrogen Sorptiometry and Electron Microscopy Studies

2002 ◽  
Vol 20 (7) ◽  
pp. 619-632 ◽  
Author(s):  
A.A. Ali ◽  
F.A. Al-Sagheer ◽  
M.I. Zaki
Keyword(s):  
Electron Microscopy ◽  
Chemical Composition ◽  
Surface Texture ◽  
Particle Morphology ◽  
High Resolution Electron Microscopy ◽  
Surface Chemical ◽  
Hydrothermal Conditions ◽  
X Ray ◽  
Surface Chemical Composition ◽  
Resolution Electron

Three different modifications of manganese(IV) oxide, viz. cryptomelane, nsutite and todorokite-like, were synthesized by hydrothermal methods. The bulk chemical composition, phase composition, crystalline structure and particle morphology of the resulting materials were determined by thermogravimetry, atomic absorption spectroscopy, X-ray diffractometry, infrared spectroscopy and scanning electron microscopy. The surface chemical composition, texture and structure were assessed using X-ray photoelectron microscopy, nitrogen sorptiometry and high-resolution electron microscopy. The results highlighted the hydrothermal conditions under which such tunnel-structured modifications of manganese(IV) oxide can be successfully synthesized. Moreover, they revealed that (i) the bulk was microcrystalline, (ii) the crystallites were either fibrils (cryptomelane and nsutite) or rod-like (todorokite) with low-index exposed facets, (iii) the surface chemical composition mostly reflected that of the bulk and (iv) the surface texture was linked with high specific areas, slit-shaped mesopores associated with particle interstices and micropores which allowed surface accessibility to the bulk tunnels of the test oxides. The application of such test oxides as shape-selective oxidation catalysts appears worthy of investigation.

Obtaining of Ni Base Intermetallic Alloys by Solidification Control

2007 ◽  
Vol 23 ◽  
pp. 283-386
Author(s):  
Mariana Lucaci ◽  
Radu L. Orban ◽  
M. Lazarescu ◽  
Stefania Gavriliu ◽  
Magdalena Lungu ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Directional Solidification ◽  
Induction Furnace ◽  
Vacuum Induction Furnace ◽  
Surface Chemical ◽  
Intermetallic Alloys ◽  
Surface Chemical Composition ◽  
Master Alloys ◽  
Solidification Control ◽  
Cylindrical Samples

Directional solidification techniques have been applied to produce Ni based intermetallic alloys with preferentially oriented columnar crystals extended along the complete length and parallel to the solidification direction. Enhanced ductility is expected from such alloys. In this paper we present the research results concerning the application of this technique to some complex Ni3Al- Fe-B alloys obtained from compacted mixtures of elemental powders. The corresponding master alloys have been obtained in a vacuum induction furnace by the known Exo-Melt process [1]. The directional solidification of these alloys was subsequently performed on cylindrical samples, at two solidification rates, 30 and 15 mm/h. The influence of the rate and composition used on the dimensional variations, densities, microstructure, constituent phases and lattice parameters, as well as on the surface chemical composition have been documented and are presented in the paper.

Zooming in on surface chemical composition of soil microaggregates – Is there an effect of plants (Festuca)?

2021 ◽  
Author(s):  
Susanne K Woche ◽  
Stefan Dultz ◽  
Robert Mikutta ◽  
Klaus Kaiser ◽  
Georg Guggenberger
Keyword(s):  
Contact Angle ◽  
Organic Matter ◽  
Chemical Composition ◽  
Photoelectron Spectroscopy ◽  
Bare Soil ◽  
Organic N ◽  
Initial Contact ◽  
Surface Chemical ◽  
Surface Chemical Composition ◽  
Fresh Organic Matter

<p>Formation of soil microaggregates (SMA) is a surface-driven process and depends on mineral cementing and organic gluing agents. Yet, the role of plants in soil microaggregation by input of fresh organic matter remains little understood. In a mesocosm experiment silty Luvisol topsoil (<250 µm; original soil material) was incubated in absence (bare soil) and presence of plants (Festuca) and water-stable free and occluded SMA were isolated after 4, 12, and 30 weeks and investigated for the surface chemical composition by X-ray photoelectron spectroscopy (XPS) and for wetting properties by contact angle determination.</p><p>Compared to the original soil, the surfaces of both free and occluded SMA tended to smaller O and larger C contents, thus a smaller O/C ratio, along with a slight increase in initial contact angle from about 10° (original soil) to about 20° (SMA). The O/C ratio decreased slightly further from 4 to 12 weeks, especially for bare soil without plants. Slightly greater C contents were detected for occluded than for free SMA, probably hinting at higher retention of organic matter on surfaces of microaggregates entrained in larger soil structures. For bare soil, a slightly greater N content was observed for free SMA while in the presence of Festuca free and occluded SMA had same N contents.</p><p>Regardless of the presence of Festuca, C speciation indicated a lower proportion (in % of total C) of C=O/O-C-O and a higher proportion of C - C/C -  H species for occluded than for free SMA, probably indicating less altered organic matter at the surfaces of occluded SMA. While the proportion of C=O/O-C-O species slightly decreased, that of C- C/C-H species slightly increased towards the end of the incubation. This may hint at some preferences in microbial respiration with respect to C compounds and formation of microbial metabolites. From N speciation a higher ratio between protonated and non-protonated organic N species (N<sub>p</sub>/N<sub>np</sub>) was indicated for Festuca than for bare soil after 4 and for 30 weeks of incubation, i.e., the presence of plants seems to impact N compounds present. The N<sub>p</sub>/N<sub>np </sub>ratio tended to decrease after 30 weeks compared to 4 weeks for both treatments, hinting on changes in N species present.</p><p>In summary, aside some effect on N species present, results indicate rather incubation and SMA origin (free, occluded) than the presence of plants (Festuca) to impact surface chemical composition of the tested SMA. This suggests no defined contribution of plants and their products to formation of 250-53 µm-sized SMA.</p>

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