Surface chemical composition of SiC-cored nanowires investigated at room and elevated temperatures in ultra-high vacuum

Vacuum ◽  
2012 ◽  
Vol 86 (12) ◽  
pp. 1974-1978 ◽  
Author(s):  
Adam Busiakiewicz ◽  
Andrzej Huczko ◽  
Michal Soszynski ◽  
Krzysztof Polanski ◽  
Rogala Maciej ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Elevated Temperatures ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Surface Chemical ◽  
Surface Chemical Composition

Surface Chemical Analysis of Nanoparticles for Commercial Products and Devices

2013 ◽  
Vol 1533 ◽  
Author(s):  
Marie-Isabelle Baraton
Keyword(s):  
Chemical Composition ◽  
Surface Chemistry ◽  
Surface Analysis ◽  
Surface Composition ◽  
High Vacuum ◽  
Surface Reactivity ◽  
Ultra High Vacuum ◽  
Ambient Atmosphere ◽  
Surface Chemical ◽  
Surface Chemical Composition

ABSTRACTAmongst the list of the measurands specific to nanoparticles, size and shape definitely matter but surface chemistry is also often cited. While it is now largely recognized that surface composition, structure and reactivity are perhaps the dominant parameters controlling properties of nanoparticles, surface chemistry is one of the key characteristics of nanoparticles which is seldom or inappropriately evaluated, as it has been identified by international organizations (such as ISO, BIPM or CEN). The usual techniques for surface analysis of materials often require ultra-high vacuum (UHV) conditions and are hardly applicable to nanoparticles. Moreover, because the surface chemical composition and reactivity are dependent on the environmental conditions, the results obtained under UHV cannot be extrapolated to nanoparticles in ambient atmosphere or dispersed in liquids.After an analysis of the stakes and challenges in the surface characterization of nanoparticles and a very brief overview of the usual techniques for surface studies, this paper presents the performance of Fourier transform infrared (FTIR) spectroscopy to investigate surface chemical composition, surface reactivity and surface functionalization of nanoparticles. As illustrating examples, the results of the FTIR surface analysis of different kinds of ceramic nanoparticles are discussed with regard to several fields of applications.

SYNTHESIS AND DEGRADATION OF THE PbS NANOPARTICLE PHOSPHORS EMBEDDED IN SiO2 (SiO2:PbS)

2007 ◽  
Vol 14 (04) ◽  
pp. 697-701 ◽  
Author(s):  
M. S. DHLAMINI ◽  
J. J. TERBLANS ◽  
O. M. NTWAEABORWA ◽  
H. C. SWART
Keyword(s):  
Chemical Composition ◽  
Fiber Optics ◽  
Photoelectron Spectroscopy ◽  
Energy Dispersive Spectrometer ◽  
Sol Gel ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Beam Current Density ◽  
Surface Chemical ◽  
Pbs Nanoparticle

PbS nanoparticle phosphors embedded in SiO 2 were synthesized at room temperature by the sol–gel method. The as-prepared SiO 2:0.134 mol% PbS nanoparticles were ground and annealed in atmosphere. Changes in the cathodoluminescence (CL) brightness and the surface chemical composition of the SiO 2:0.134 mol% PbS nanoparticle powders were investigated using a Fiber Optics PC2000 spectrometer for CL and Auger Electron Spectroscopy (AES) and X-ray Photoelectron Spectroscopy (XPS) for the surface chemical analysis. The chemical composition of the powders was analyzed by an energy-dispersive spectrometer (EDS). The CL intensity decreased when the powders were irradiated with a beam of electrons at 2 keV energy and a beam current density of 54 mA/cm2 in an ultra-high vacuum chamber at oxygen ( O 2) pressures ranging between 5 × 10-8 and 2 × 10-7 Torr for several hours. The O 2 Auger peak-to-peak height (APPH) decreased as the CL intensity decreased. XPS analysis on the degraded spot showed the development of characteristic SiO , SiO x, and elemental Si peaks on the low-energy side of the SiO 2 peak. The desorption of O 2 from the surface, which resulted in a decrease in the CL intensity is attributed to the dissociation of SiO 2 into elemental Si and O 2 by the electron bombardment. The degradation was less severe at higher oxygen pressures. PbSO 4 was also formed on the surface during the electron beam degradation process.

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.

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