A different chemical route to prepare hafnium diboride‐based nanofibers: Effect of chemical composition

2020 ◽  
Vol 17 (5) ◽  
pp. 2123-2136
Author(s):  
Raziyeh Ghelich ◽  
Hossein Abdizadeh ◽  
Mohammad Reza Jahannama ◽  
Fatemeh Sadat Torknik ◽  
Mohammad Reza Vaezi
Keyword(s):  
Chemical Composition ◽  
Hafnium Diboride ◽  
Chemical Route

Chemical inventory of Class I protostars with IRAM-30m: A bridge between protostars and planet-forming disks

2020 ◽  
Author(s):  
Seyma Mercimek ◽  
Claudio Codella ◽  
Linda Podio ◽  
Eleonora Bianchi ◽  
Layal Chahine ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Spatial Scales ◽  
Protoplanetary Disks ◽  
Abundance Ratio ◽  
Point Of View ◽  
Class I ◽  
Forming Process ◽  
Chemical Route ◽  
Star Forming ◽  
Order Of Magnitude

<p>Understanding how molecular complexity varies in Sun-like star forming regions is mandatory to comprehend whether the chemical composition of the protostellar stages is inherited by protoplanetary disks and planets. In this perspective, our ambitious overall goal is to follow the chemical evolution from the earliest protostellar stages to the relics of our pristin Solar System, i.e. comets. We investigate the chemical composition of Class I protostars, with a typical age of 10<sup>5</sup> yr. Class I sources represent a bridge between Class 0 protostars (about 10<sup>4</sup> yr), where the bulk of the material that eventually form the protostar is still in the envelope, and the Class II protoplanetary disks (10<sup>6</sup> yr). The importance of the Class I stage has been recently strengthened by recent ALMA images showing that planet formation occurs already in disks with ages < 1 Myr. Unfortunately, only very few Class I sources, e.g. SVS13-A and Ser-17, have been chemically characterized through spectral survey at millimeter wavelengths. Therefore, we are still far to conclude if Class I protostars are also a bridge from a chemical point of view.</p><p>In this context, and in the framework of the H2020 MSCA ITN Project AstroChemical Origins (www.aco-itn.org), we present a chemical census of 4 Class I sources: L1551-IRS5, L1489-IRS (in the Taurus star forming region) and B5-IRS1, L1455-IRS1 (in Perseus). We used IRAM 30m single-dish observations at 1.3 mm sampling spatial scales of 1500-2500 au. We detect up to 80 lines (depending on the source) due to 27 species: from simple molecules (e.g. S-bearing: OCS, H<sub>2</sub>S, CCS, H<sub>2</sub>CS,  N-bearing: CN, HNCO, C-chains: c-C<sub>3</sub>H<sub>2</sub>, c-C<sub>3</sub>H, D-species: CCD, DCN, D<sub>2</sub>CO, CH<sub>2</sub>DOH, ions: N<sub>2</sub>D<sup>+</sup>, DCO<sup>+</sup>) to the so called interstellar Complex Organic Molecules (iCOMs), which can be considered as the bricks of a prebiotic chemistry (H<sub>2</sub>CO, H<sub>2</sub>CCO, CH<sub>3</sub>OH, CH<sub>3</sub>CN, CH<sub>3</sub>CHO, CH<sub>3</sub>CCH, HCOOCH<sub>3</sub>).</p><p> </p><p>All the sources are associated with high-velocity CO, H<sub>2</sub>CO, and SO outflows. In addition, our observations show a chemical differentiation, that can be summarized as follows: (1) we detect hot corino chemistry in one source, L1551 -IRS5, revealed by iCOMs as well as OCS, H<sub>2</sub>S, which could be the main S-bearing carriers on icy grains; (2) the envelopes of all the protostars are rich of carbon-chains molecules; (3) we find that the iCOMs of L1551 have similar abundance ratio, within one order of magnitude, as Class 0 and Class I hot corinos previously observed. </p><p> </p><p>We also compare the iCOMs abundance ratios as measured in the Class I source L1551-IRS5 with those measured in comets Hale-Bopp, Lemmon, Lovejoy, and 67P to understand if the cometary composition is inherited from the previous evolutionary stages. We find that the iCOMs abundance ratio (e.g. CH3CHO/HCOOCH3) at the Class 0 and Class I protostellar stages is comparable with that of comets, suggesting that cometary material could be inherited from the early stages of the star forming process leading to a Sun-like star. These results are a basis to future follow-up interferometric observations aimed to obtain a full inventory of the chemistry of Class I sources and to reconstruct the chemical route from Class 0 protostars to protoplanetary disks and planets.</p><p><br><br><br><br></p>

Synthesis and Characterization of SnS Nanoparticles through a Non-Aqueous Chemical Route for Depositing Photovoltaic Absorber Layers

2014 ◽  
Vol 28 ◽  
pp. 91-99 ◽  
Author(s):  
Mou Pal ◽  
A. Martinez Ayala ◽  
N.R. Mathews ◽  
X. Mathew
Keyword(s):  
Optical Properties ◽  
Chemical Composition ◽  
Near Infrared ◽  
Blue Shift ◽  
Xrd Analysis ◽  
Optical Absorption Spectroscopy ◽  
Complexing Agent ◽  
Chemical Route ◽  
X Ray ◽  
Glass Substrates

SnS nanocrystals of sub-10 nm in size were synthesized by a room temperature, non-aqueous chemical route in the presence of different amounts of triethanolamine (TEA) used as a complexing agent. The crystallinity, size, morphology, chemical composition and optical properties of the as-prepared SnS nanoparticles were investigated by powder X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Energy-dispersive X-ray spectroscopy (EDS), micro Raman and optical absorption spectroscopy. The XRD analysis and HRTEM investigation of SnS nanoparticles confirmed the presence of crystalline orthorhombic SnS phase. Upon increasing the amount of TEA, the crystallite size of the samples decreased gradually showing evidence of quantum confinement. EDS analysis showed that SnS nanoparticles (NPs) grown in absence of TEA were highly stoichiometric whereas in TEA capped samples, the atomic concentration of S is slightly higher than that of Sn. As-synthesized SnS nanocrystals displayed strong absorption in the visible and near-infrared spectral regions followed by a blue shift of their absorption edge on increasing the TEA concentration. These nanoparticles were used to prepare SnS paste which was deposited on conducting glass substrates to obtain thin films for photovoltaic applications. The crystallinity, morphology, chemical composition and optical properties of annealed SnS films were investigated.

The Origin of the Moon

1962 ◽  
Vol 14 ◽  
pp. 149-155 ◽  
Author(s):  
E. L. Ruskol
Keyword(s):  
Chemical Composition ◽  
Solar System ◽  
The Moon ◽  
The Earth ◽  
The Difference ◽  
Origin Of The Moon

The difference between average densities of the Moon and Earth was interpreted in the preceding report by Professor H. Urey as indicating a difference in their chemical composition. Therefore, Urey assumes the Moon's formation to have taken place far away from the Earth, under conditions differing substantially from the conditions of Earth's formation. In such a case, the Earth should have captured the Moon. As is admitted by Professor Urey himself, such a capture is a very improbable event. In addition, an assumption that the “lunar” dimensions were representative of protoplanetary bodies in the entire solar system encounters great difficulties.

On the Inhomogeneity of Chemical Composition over the Surface of 21 Per

1976 ◽  
Vol 32 ◽  
pp. 343-349
Author(s):  
Yu.V. Glagolevsky ◽  
K.I. Kozlova ◽  
V.S. Lebedev ◽  
N.S. Polosukhina
Keyword(s):  
Chemical Composition ◽  
Spectral Line ◽  
Variable Star ◽  
Radial Velocities ◽  
Crimean Astrophysical Observatory ◽  
Line Intensities ◽  
Magnetic Variable

SummaryThe magnetic variable star 21 Per has been studied from 4 and 8 Å/mm spectra obtained with the 2.6 - meter reflector of the Crimean Astrophysical Observatory. Spectral line intensities (Wλ) and radial velocities (Vr) have been measured.

Structural Studies on Mitotic Spindle Fibres

1978 ◽  
Vol 36 (3) ◽  
pp. 615-626
Author(s):  
J.R. Mcintosh
Keyword(s):  
Chemical Composition ◽  
Mitotic Spindle ◽  
Structural Studies ◽  
Mitotic Apparatus ◽  
Chemical Studies ◽  
Medical Interest ◽  
Spindle Fibres

The mitotic apparatus is a structure of obvious biological and medical interest, but it has proved to be a difficult cellular machine to understand. The chemical composition of the spindle is only slightly elucidated, largely because of the difficulties in preparing useful isolates of the structure. Chemical studies of the mitotic spindle have been reviewed elsewhere (Mcintosh, 1977), and will not be discussed further here. One would think that structural studies on the mitotic apparatus (MA) in situ would be straightforward, but even with this approach there is some disagreement in the results obtained with various methods and by different investigators. In this paper I will review briefly the approaches which have been used in structural studies of the MA, pointing out the strengths and problems of each approach. I will summarize the principal findings of the different methods, and identify what seem to be fruitful avenues for further work.

Effects of 5-5'-Diphenyl-2-thiohydantoin (DPTH) and Thyroxine on the Ultrastructure and Chemical Composition of Rat Liver

1971 ◽  
Vol 29 ◽  
pp. 570-571
Author(s):  
E. A. Elfont ◽  
R. B. Tobin ◽  
D. G. Colton ◽  
M. A. Mehlman
Keyword(s):  
Chemical Composition ◽  
Rat Liver ◽  
Future Study ◽  
Mode Of Action ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Effective Inhibitor ◽  
Biochemical Effects ◽  
Glycerophosphate Dehydrogenase ◽  
Stimulation Of

Summary5,-5'-diphenyl-2-thiohydantoin (DPTH) is an effective inhibitor of thyroxine (T4) stimulation of α-glycerophosphate dehydrogenase in rat liver mitochondria. Because this finding indicated a possible tool for future study of the mode of action of thyroxine, the ultrastructural and biochemical effects of DPTH and/or thyroxine on rat liver mere investigated.Rats were fed either standard or DPTH (0.06%) diet for 30 days before T4 (250 ug/kg/day) was injected. Injection of T4 occurred daily for 10 days prior to sacrifice. After removal of the liver and kidneys, part of the tissue was frozen at -50°C for later biocheailcal analyses, while the rest was prefixed in buffered 3.5X glutaraldehyde (390 mOs) and post-fixed in buffered 1Z OsO4 (376 mOs). Tissues were embedded in Araldlte 502 and the sections examined in a Zeiss EM 9S.Hepatocytes from hyperthyroid rats (Fig. 2) demonstrated enlarged and more numerous mitochondria than those of controls (Fig. 1). Glycogen was almost totally absent from the cytoplasm of the T4-treated rats.

Applications of Photoelectron Microscopy

1976 ◽  
Vol 34 ◽  
pp. 506-507
Author(s):  
William J. Baxter
Keyword(s):  
Electron Microscopy ◽  
Thermal Decomposition ◽  
Chemical Composition ◽  
Ultraviolet Radiation ◽  
Thin Layer ◽  
Edge Effects ◽  
Electron Optics ◽  
Surface Layers ◽  
Crystalline Orientation ◽  
Fluorescent Screen

In this form of electron microscopy, photoelectrons emitted from a metal by ultraviolet radiation are accelerated and imaged onto a fluorescent screen by conventional electron optics. image contrast is determined by spatial variations in the intensity of the photoemission. The dominant source of contrast is due to changes in the photoelectric work function, between surfaces of different crystalline orientation, or different chemical composition. Topographical variations produce a relatively weak contrast due to shadowing and edge effects.Since the photoelectrons originate from the surface layers (e.g. ∼5-10 nm for metals), photoelectron microscopy is surface sensitive. Thus to see the microstructure of a metal the thin layer (∼3 nm) of surface oxide must be removed, either by ion bombardment or by thermal decomposition in the vacuum of the microscope.

Thermomechanical Treatment of a 4340 Ni-Cr-Mo Alloy Steel

1981 ◽  
Vol 39 ◽  
pp. 314-315 ◽  
Author(s):  
M.T. Jahn ◽  
J.C. Yang ◽  
C.M. Wan
Keyword(s):  
Mechanical Property ◽  
Chemical Composition ◽  
Alloy Steel ◽  
Thermomechanical Treatment ◽  
Room Temperature ◽  
Good Combination ◽  
Thermal Treatments ◽  
Low Carbon ◽  
4340 Steel ◽  
Good Improvement

4340 Ni-Cr-Mo alloy steel is widely used due to its good combination of strength and toughness. The mechanical property of 4340 steel can be improved by various thermal treatments. The influence of thermomechanical treatment (TMT) has been studied in a low carbon Ni-Cr-Mo steel having chemical composition closed to 4340 steel. TMT of 4340 steel is rarely examined up to now. In this study we obtain good improvement on the mechanical property of 4340 steel by TMT. The mechanism is explained in terms of TEM microstructures4340 (0.39C-1.81Ni-0.93Cr-0.26Mo) steel was austenitized at 950°C for 30 minutes. The TMTed specimen (T) was obtained by forging the specimen continuously as the temperature of the specimen was decreasing from 950°C to 600°C followed by oil quenching to room temperature. The thickness reduction ratio by forging is 40%. The conventional specimen (C) was obtained by quenching the specimen directly into room temperature oil after austenitized at 950°C for 30 minutes. All quenched specimens (T and C) were then tempered at 450, 500, 550, 600 or 650°C for four hours respectively.

Application Of Electron Probe Analyses Of Minerals In Discussing The Relationship Between Ductile Deformation And Metamorphism

1990 ◽  
Vol 48 (2) ◽  
pp. 250-251
Author(s):  
Fan Guochuan ◽  
Sun Zhongshi
Keyword(s):  
Chemical Composition ◽  
Shear Deformation ◽  
Electron Probe ◽  
General Rule ◽  
Granulite Facies ◽  
Ductile Deformation ◽  
Higher Temperature ◽  
Ductile Shear ◽  
The Relationship ◽  
Ductile Shear Deformation

Under influence of ductile shear deformation, granulite facies mineral paragenesis underwent metamorphism and changes in chemical composition. The present paper discusses some changes in chemical composition of garnet in hypers thene_absent felsic gnesiss and of hypersthene in rock in early and late granulite facies undergone increasing ductile shear deformation .In garnet fetsic geniss, band structures were formed because of partial melting and resulted in zoning from massive⟶transitional⟶melanocrate zones in increasing deformed sequence. The electron-probe analyses for garnet in these zones are listed in table 1 . The Table shows that Mno, Cao contents in garnet decrease swiftly from slightly to intensely deformed zones.In slightly and moderately deformed zones, Mgo contents keep unchanged and Feo is slightly lower. In intensely deformed zone, Mgo contents increase, indicating a higher temperature. This is in accord with the general rule that Mgo contents in garnet increase with rising temperature.

Structures of chemically stabilized ceramics

1993 ◽  
Vol 51 ◽  
pp. 924-925
Author(s):  
Pratibha L. Gai ◽  
M. A. Saltzberg ◽  
L.G. Hanna ◽  
S.C. Winchester
Keyword(s):  
High Temperature ◽  
Calcium Nitrate ◽  
Nitrate Hexahydrate ◽  
Chemical Route ◽  
Cubic Form ◽  
Tetragonal Form ◽  
Wet Chemical ◽  
Wet Chemical Route ◽  
Final Composition ◽  
Aluminium Nitrate Nonahydrate

Silica based ceramics are some of the most fundamental in crystal chemistry. The cristobalite form of silica has two modifications, α (low temperature, tetragonal form) and β (high temperature, cubic form). This paper describes our structural studies of unusual chemically stabilized cristobalite (CSC) material, a room temperature silica-based ceramic containing small amounts of dopants, prepared by a wet chemical route. It displays many of the structural charatcteristics of the high temperature β-cristobalite (∼270°C), but does not undergo phase inversion to α-cristobalite upon cooling. The Structure of α-cristobalite is well established, but that of β is not yet fully understood.Compositions with varying Ca/Al ratio and substitutions in cristobalite were prepared in the series, CaO:Al2O3:SiO2 : 3-x: x : 40, with x= 0-3. For CSC, a clear sol was prepared from Du Pont colloidal silica, Ludox AS-40®, aluminium nitrate nonahydrate, and calcium nitrate hexahydrate in proportions to form a final composition 1:2:40 composition.

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