X-ray extinction from interstellar dust

Aims. We present a study on the prospects of observing carbon, sulfur, and other lower abundance elements (namely Al, Ca, Ti, and Ni) present in the interstellar medium using future X-ray instruments. We focus in particular on the detection and characterization of interstellar dust along the lines of sight. Methods. We compared the simulated data with different sets of dust aggregates, either obtained from past literature or measured by us using the SOLEIL-LUCIA synchrotron beamline. Extinction by interstellar grains induces modulations of a given photolelectric edge, which can be in principle traced back to the chemistry of the absorbing grains. We simulated data of instruments with characteristics of resolution and sensitivity of the current Athena, XRISM, and Arcus concepts. Results. In the relatively near future, the depletion and abundances of the elements under study will be determined with confidence. In the case of carbon and sulfur, the characterization of the chemistry of the absorbing dust will be also determined, depending on the dominant compound. For aluminum and calcium, despite the large depletion in the interstellar medium and the prominent dust absorption, in many cases the edge feature may not be changing significantly with the change of chemistry in the Al- or Ca-bearing compounds. The exinction signature of large grains may be detected and modeled, allowing a test on different grain size distributions for these elements. The low cosmic abundance of Ti and Ni will not allow us a detailed study of the edge features.

Download Full-text

Modelling the properties of interstellar dust using the Si K-edge

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320000332 ◽

2019 ◽

Vol 15 (S350) ◽

pp. 259-263

Author(s):

Sascha Zeegers ◽

Elisa Costantini ◽

Daniele Rogantini ◽

Cor de Vries ◽

Harald Mutschke ◽

...

Keyword(s):

Interstellar Medium ◽

Cross Sections ◽

Interstellar Dust ◽

X Rays ◽

X Ray ◽

Synchrotron Facility ◽

The Galaxy ◽

Main Components ◽

Distribution Composition ◽

X Ray Binaries

AbstractThe properties of interstellar dust (ID) can be studied in great detail by making use of X-ray spectroscopy techniques. The radiation of X-rays sources is scattered and absorbed by dust grains in the interstellar medium. The X-ray band is especially suitable to study silicates - one of the main components of ID -since it contains the absorption edges of Si, Mg, O and Fe. In the Galaxy, we can use absorption features in the spectra of X-ray binaries to study the size distribution, composition and crystalline structure of grains. In order to derive these properties, it is necessary to acquire a database of detailed extinction cross sections models, that reflects the composition of the dust in the interstellar medium. We present the extinction profiles of a set of newly acquired measurements of 14 dust analogues at the Soleil Synchrotron facility in Paris, where we focus on silicates and the Si-K edge in particular, which is modelled with unprecedented accuracy. These models are used to analyse ID in the dense environments of the Galaxy.

Download Full-text

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100071107 ◽

1973 ◽

Vol 31 ◽

pp. 132-133 ◽

Cited By ~ 1

Author(s):

R. E. Herfert

Keyword(s):

Surface Characterization ◽

Analytical Techniques ◽

X Ray Diffraction ◽

Depth Of Penetration ◽

X Ray ◽

The Past ◽

Transmission Electron ◽

Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

Download Full-text

High Resolution Replication of Organoclay Surfaces

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100055126 ◽

1982 ◽

Vol 40 ◽

pp. 576-577

Author(s):

W. W. Barker ◽

W. E. Rigsby ◽

V. J. Hurst ◽

W. J. Humphreys

Keyword(s):

Clay Mineral ◽

Organic Molecule ◽

Organic Molecules ◽

X Ray Diffraction ◽

Xrd Pattern ◽

X Ray ◽

Naturally Occurring ◽

Silicate Layers ◽

Mineral Identification

Experimental clay mineral-organic molecule complexes long have been known and some of them have been extensively studied by X-ray diffraction methods. The organic molecules are adsorbed onto the surfaces of the clay minerals, or intercalated between the silicate layers. Natural organo-clays also are widely recognized but generally have not been well characterized. Widely used techniques for clay mineral identification involve treatment of the sample with H2 O2 or other oxidant to destroy any associated organics. This generally simplifies and intensifies the XRD pattern of the clay residue, but helps little with the characterization of the original organoclay. Adequate techniques for the direct observation of synthetic and naturally occurring organoclays are yet to be developed.

Download Full-text

Digital x-ray mapping of nanometer-size supported bimetallic catalysts

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100104716 ◽

1988 ◽

Vol 46 ◽

pp. 530-531

Author(s):

L. T. Germinario

Keyword(s):

Background Radiation ◽

Metal Cluster ◽

Single Element ◽

Beam Diameter ◽

X Rays ◽

X Ray ◽

Major Interest ◽

Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

Download Full-text

Plant Pathology Diagnosed by X-Ray Microanalysis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100129152 ◽

1987 ◽

Vol 45 ◽

pp. 974-975

Author(s):

J. H. Resau ◽

N. Howell ◽

S. H. Chang

Keyword(s):

Electron Microscopy ◽

Plant Pathology ◽

Biochemical Characterization ◽

Nutrient Deficiency ◽

Green Leaf ◽

Parasitic Infestation ◽

X Ray

Spinach grown in Texas developed “yellow spotting” on the peripheral portions of the leaves. The exact cause of the discoloration could not be determined as there was no evidence of viral or parasitic infestation of the plants and biochemical characterization of the plants did not indicate any significant differences between the yellow and green leaf portions of the spinach. The present study was undertaken using electron microscopy (EM) to determine if a micro-nutrient deficiency was the cause for the discoloration.Green leaf spinach was collected from the field and sent by express mail to the EM laboratory. The yellow and equivalent green portions of the leaves were isolated and dried in a Denton evaporator at 10-5 Torr for 24 hrs. The leaf specimens were then examined using a JEOL 100 CX analytical microscope. TEM specimens were prepared according to the methods of Trump et al.

Download Full-text

EXELFS Studies of Carbon Fibers

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100133953 ◽

1990 ◽

Vol 48 (2) ◽

pp. 72-73

Author(s):

V. Serin ◽

K. Hssein ◽

G. Zanchi ◽

J. Sévely

Keyword(s):

Carbon Fibers ◽

Energy Analysis ◽

Electron Excitation ◽

Complex Structures ◽

High Modulus ◽

Promising Technique ◽

X Ray ◽

Fine Structures ◽

X Ray Absorption

The present developments of electron energy analysis in the microscopes by E.E.L.S. allow an accurate recording of the spectra and of their different complex structures associated with the inner shell electron excitation by the incident electrons (1). Among these structures, the Extended Energy Loss Fine Structures (EXELFS) are of particular interest. They are equivalent to the well known EXAFS oscillations in X-ray absorption spectroscopy. Due to the EELS characteristic, the Fourier analysis of EXELFS oscillations appears as a promising technique for the characterization of composite materials, the major constituents of which are low Z elements. Using EXELFS, we have developed a microstructural study of carbon fibers. This analysis concerns the carbon K edge, which appears in the spectra at 285 eV. The purpose of the paper is to compare the local short range order, determined by this way in the case of Courtauld HTS and P100 ex-polyacrylonitrile carbon fibers, which are high tensile strength (HTS) and high modulus (HM) fibers respectively.

Download Full-text

Characterization of defects in tabular silver halide grains

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100178367 ◽

1990 ◽

Vol 48 (4) ◽

pp. 1046-1047

Author(s):

C. Goessens ◽

D. Schryvers ◽

J. Van Landuyt ◽

A. Verbeeck ◽

R. De Keyzer

Keyword(s):

Radiation Damage ◽

Silver Halide ◽

Chemical Characteristics ◽

X Ray ◽

Free Region ◽

Central Defect ◽

Crystallographic Defects ◽

Physical And Chemical ◽

Two Sides

Silver halide grains (AgX, X=Cl,Br,I) are commonly recognized as important entities in photographic applications. Depending on the preparation specifications one can grow cubic, octahedral, tabular a.o. morphologies, each with its own physical and chemical characteristics. In the present study crystallographic defects introduced by the mixing of 5-20% iodide in a growing AgBr tabular grain are investigated. X-ray diffractometry reveals the existence of a homogeneous Ag(Br1-xIx) region, expected to be formed around the AgBr kernel. In fig. 1 a two-beam BF image, taken at T≈100 K to diminish radiation damage, of a triangular tabular grain is presented, clearly showing defect contrast fringes along four of the six directions; the remaining two sides show similar contrast under relevant diffraction conditions. The width of the central defect free region corresponds with the pure AgBr kernel grown before the mixing with I. The thickness of a given grain lies between 0.15 and 0.3 μm: as indicated in fig. 2 triangular (resp. hexagonal) grains exhibit an uneven (resp. even) number of twin interfaces (i.e., between + and - twin variants) parallel with the (111) surfaces. The thickness of the grains and the existence of the twin variants was confirmed from CTEM images of perpendicular cuts.

Download Full-text

PRONAOS observations of the interstellar medium: New insights on interstellar Dust

EAS Publications Series ◽

10.1051/eas:2002054 ◽

2002 ◽

Vol 4 ◽

pp. 9-9

Author(s):

I. Ristorcelli ◽

B. Stepnik ◽

X. Dupac ◽

A. Abergel ◽

J. P. Bernard ◽

...

Keyword(s):

Interstellar Medium ◽

Interstellar Dust

Download Full-text

Synthesis and characterization of TiN / Ti / AISI 410 coatings

Journal of Sciences and Engineering ◽

10.32829/sej.v2i1.54 ◽

2018 ◽

Vol 2 (1) ◽

pp. 7

Author(s):

S Chirino ◽

Jaime Diaz ◽

N Monteblanco ◽

E Valderrama

Keyword(s):

Synthesis And Characterization ◽

Photoemission Spectroscopy ◽

X Ray Diffraction ◽

X Ray ◽

Columnar Grains ◽

Tin Thin Films ◽

Steel Aisi ◽

Interacting Surfaces ◽

Stainless Steel Aisi

The synthesis and characterization of Ti and TiN thin films of different thicknesses was carried out on a martensitic stainless steel AISI 410 substrate used for tool manufacturing. The mechanical parameters between the interacting surfaces such as thickness, adhesion and hardness were measured. By means of the scanning electron microscope (SEM) the superficial morphology of the Ti/TiN interface was observed, finding that the growth was of columnar grains and by means of EDAX the existence of titanium was verified. Using X-ray diffraction (XRD) it was possible to observe the presence of residual stresses (~ -3.1 GPa) due to the different crystalline phases in the coating. Under X-ray photoemission spectroscopy (XPS) it was possible to observe the molecular chemical composition of the coating surface, being Ti-N, Ti-N-O and Ti-O the predominant ones.

Download Full-text