Spectroscopic Characterization of the Nitridation Process of Polymeric Precursors to SI-M-N-O Systems (M=Ti, Zr, Al)

1992 ◽  
Vol 287 ◽  
Author(s):  
F. Babonneau ◽  
G. D. Soraru
Keyword(s):  
Spectroscopic Characterization ◽  
Ceramic Materials ◽  
Spectroscopic Techniques ◽  
X Ray ◽  
Nitridation Process ◽  
Local Environments ◽  
Ceramic Precursors ◽  
Mixed Ceramic ◽  
X Ray Absorption

ABSTRACTA commercial polycarbosilane was modified with various metallic alkoxides to get mixed ceramic precursors in the Si-M-C-O systems (M=Ti, Zr Al). Pyrolysis under ammonia leads to the formation of various ceramic materials depending on the nature of M : Si3N4/TiN, Si3N4/ZrO2 or β′-SiAlON phases.The polymer-to-ceramics conversion have been studied by MAS-NMR (29 Si, 27Al) and X-ray absorption (Ti K-edge). This paper will show how these two complementary spectroscopic techniques can be used to follow the nitridation process by probing local environments of different elements. In addition, it will be pointed out how X-ray absorption can be a powerful tool for the detection of the crystallization of nitride cubic phases.

Spectroscopic Characterization of a Pre-Ceramic Polymer For Sic/Tic System.

1990 ◽  
Vol 180 ◽  
Author(s):  
Florence Babonneau ◽  
Patrice Barre ◽  
Jacques Livage ◽  
Michel Verdaguer
Keyword(s):  
Spectroscopic Characterization ◽  
Argon Atmosphere ◽  
Mas Nmr ◽  
Spectroscopic Techniques ◽  
Excess Carbon ◽  
X Ray ◽  
Local Environments ◽  
X Ray Absorption ◽  
Cp Mas Nmr

ABSTRACTPolytitanocarbosilane precursor for SiC/TiC ceramics was characterized by various spectroscopic techniques (29Si and 13C CP MAS NMR, Ti K-edge XANES and EXAFS) in order to follow how titanium ions are incorporated into the polycarbosilane-based polymer. This polymer has been fired in argon atmosphere, and the evolution of the local environments of Si and Ti atoms, during the pyrolysis process, have been followed using 29Si MAS-NMR and Ti K-edge X-ray absorption: this study reveals the formation of Si-O bonds above 500°C, while Ti-C bonds clearly appear around 800°C. Above 1000°C, Si-O bonds are consumed by reaction with excess carbon and the system finally crystallizes into SiC/TiC mixture above 1200°C.

scholarly journals Synthesis, Crystal Structures, and Spectroscopic Characterization of Bis-aldehyde Monomers and Their Electrically Conductive Pristine Polyazomethines

Polymers ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1498 ◽  
Author(s):  
Abdul Hafeez ◽  
Zareen Akhter ◽  
John F. Gallagher ◽  
Nawazish Ali Khan ◽  
Asghari Gul ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Spectroscopic Characterization ◽  
Spectroscopic Techniques ◽  
Conductivity Measurements ◽  
X Ray Diffraction ◽  
Electrically Conductive ◽  
X Ray ◽  
Vis Spectroscopy ◽  
Ft Ir

Bis-aldehyde monomers 4-(4′-formyl-phenoxy)benzaldehyde (3a), 3-methoxy-4-(4′-formyl-phenoxy)benzaldehyde (3b), and 3-ethoxy-4-(4′-formyl-phenoxy)benzaldehyde (3c) were synthesized by etherification of 4-fluorobenzaldehyde (1) with 4-hydroxybenzaldehyde (2a), 3-methoxy-4-hydroxybenzaldehyde (2b), and 3-ethoxy-4-hydroxybenzaldehyde (2c), respectively. Each monomer was polymerized with p-phenylenediamine and 4,4′-diaminodiphenyl ether to yield six poly(azomethine)s. Single crystal X-ray diffraction structures of 3b and 3c were determined. The structural characterization of the monomers and poly(azomethine)s was performed by FT-IR and NMR spectroscopic techniques and elemental analysis. Physicochemical properties of polymers were investigated by powder X-ray diffraction, thermogravimetric analysis (TGA), viscometry, UV–vis, spectroscopy and photoluminescence. These polymers were subjected to electrical conductivity measurements by the four-probe method, and their conductivities were found to be in the range 4.0 × 10−5 to 6.4 × 10−5 Scm−1, which was significantly higher than the values reported so far.

scholarly journals Etazene (N,N-diethyl-2-{[(4-ethoxyphenyl)methyl]-1H-benzimidazol-1-yl}-ethan-1-amine (dihydrochloride)): a novel benzimidazole opioid NPS identified in seized material: crystal structure and spectroscopic characterization

2020 ◽  
Author(s):  
Marta Siczek ◽  
Marcin Zawadzki ◽  
Miłosz Siczek ◽  
Agnieszka Chłopaś-Konowałek ◽  
Paweł Szpot
Keyword(s):  
Crystal Structure ◽  
Analytical Data ◽  
Chemical Characterization ◽  
Drug Market ◽  
Spectroscopic Characterization ◽  
Illegal Drug ◽  
Spectroscopic Techniques ◽  
X Ray ◽  
Full Characterization

Abstract Purpose The aim of the study was to present the spectroscopic characteristics and crystal structure of the etazene—a benzimidazole opioid, which appeared on the illegal drug market in Poland in the last weeks. Methods The title compound was analyzed by X-ray crystallography as well as gas and liquid chromatography combined with mass spectrometry. Spectroscopic techniques have also been used, such as nuclear magnetic resonance, infrared and ultraviolet-visible spectroscopies. Results We presented the identification and the broad chemical characterization of etazene, a synthetic opioid that has recently been introduced on the illegal drug market. Conclusions In this paper, we described single-crystal X-ray, chromatographic and spectroscopic characterization of a synthetic opioid that emerged on the new psychoactive substance (NPS) market in Poland. To the best of our knowledge, this is the first full characterization of etazene. Analytical data presented in the work can be helpful in identification and detection of the NPS in forensic and clinical laboratories.

scholarly journals Cu+-specific CopB transporter: Revising P1B-type ATPase classification

2018 ◽  
Vol 115 (9) ◽  
pp. 2108-2113 ◽  
Author(s):  
Rahul Purohit ◽  
Matthew O. Ross ◽  
Sharon Batelu ◽  
April Kusowski ◽  
Timothy L. Stemmler ◽  
...  
Keyword(s):  
Maximal Activity ◽  
Spectroscopic Characterization ◽  
Spectroscopic Studies ◽  
Divalent Metal Ions ◽  
X Ray ◽  
Reducing Environment ◽  
Methionine Residues ◽  
Cellular Copper ◽  
X Ray Absorption

The copper-transporting P1B-ATPases, which play a key role in cellular copper homeostasis, have been divided traditionally into two subfamilies, the P1B-1-ATPases or CopAs and the P1B-3-ATPases or CopBs. CopAs selectively export Cu+ whereas previous studies and bioinformatic analyses have suggested that CopBs are specific for Cu2+ export. Biochemical and spectroscopic characterization of Sphaerobacter thermophilus CopB (StCopB) show that, while it does bind Cu2+, the binding site is not the prototypical P1B-ATPase transmembrane site and does not involve sulfur coordination as proposed previously. Most important, StCopB exhibits metal-stimulated ATPase activity in response to Cu+, but not Cu2+, indicating that it is actually a Cu+ transporter. X-ray absorption spectroscopic studies indicate that Cu+ is coordinated by four sulfur ligands, likely derived from conserved cysteine and methionine residues. The histidine-rich N-terminal region of StCopB is required for maximal activity, but is inhibitory in the presence of divalent metal ions. Finally, reconsideration of the P1B-ATPase classification scheme suggests that the P1B-1- and P1B-3-ATPase subfamilies both comprise Cu+ transporters. These results are completely consistent with the known presence of only Cu+ within the reducing environment of the cytoplasm, which should eliminate the need for a Cu2+ P1B-ATPase.

Designing Zeolites As Novel Precursors To Electronic Ceramics

1991 ◽  
Vol 233 ◽  
Author(s):  
David R. Corbin ◽  
John B. Parise ◽  
Uma Chowdhry ◽  
M. A. Subramanian
Keyword(s):  
Fine Structure ◽  
Ceramic Materials ◽  
Ceramic Composites ◽  
Zeolite A ◽  
X Ray ◽  
Electronic Ceramics ◽  
Absorption Fine ◽  
Ceramic Precursors ◽  
Conventional Methods ◽  
X Ray Absorption

ABSTRACTThe decomposition of zeolites is a novel route for the synthesis of aluminosilicate-based ceramic materials. Zeolites offer a number of advantages as ceramic precursors which allow the formation of dense ceramics at lower temperatures than by conventional methods. Using various cation-exchanged zeolites, ceramics and ceramic composites containing anorthite (CaAl2Si2O8). mullite (Al6Si2O11) cordierite (Mg2Al4Si5O18). celsian (BaAl2Si2O8), and ß-spodumene (LiAlSi2O6) have been formed. Using Extended X-ray Absorption Fine Structure (EXAFS), we have studied the reconstructive transformation of strontium-exchanged zeolite A to Sr-anorthite and have shown that the primary coordination of strontium remains intact during conversion.

scholarly journals Spectroscopic Characterization of Eoholocene Bones Found in a Cave in Northeast Brazil

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
P. V. Oliveira ◽  
M. S. S. Viana ◽  
O. A. Barros ◽  
P. T. C. Freire ◽  
F. I. Bezerra ◽  
...  
Keyword(s):  
National Park ◽  
Animal Species ◽  
Spectroscopic Characterization ◽  
Spectroscopic Techniques ◽  
X Ray Diffraction ◽  
Future Studies ◽  
X Ray ◽  
Inorganic Chemical ◽  
Supply Information

The preservation of fossils depends on several interactions of organic and inorganic chemical processes. The hard parts, which are more suitable for fossilization, might record valuable information of biogenic processes, while the taphonomic characteristics supply information on postmortem chemical transformation. Here, X-ray fluorescence, X-ray diffraction, and infrared spectroscopy analyses were carried out in Early Eoholocene fragments of bones collected from the subsurface at Gruta do Urso Fóssil, Ubajara National Park, northeast of Ceará State in Brazil. It is suggested a lower degree of decomposition, a preservation of the original mineral composition, along with some incidence of encrustation, and the occurrence of different animal species are analyzed. These preliminary data serve as a basis for future studies involving fossil biota from the deposits of Gruta do Urso Fóssil using spectroscopic techniques.

Structural and spectroscopic characterization of an Fe(VI) bis(imido) complex

Science ◽  
2020 ◽  
Vol 370 (6514) ◽  
pp. 356-359 ◽  
Author(s):  
Jorge L. Martinez ◽  
Sean A. Lutz ◽  
Hao Yang ◽  
Jiaze Xie ◽  
Joshua Telser ◽  
...  
Keyword(s):  
Double Resonance ◽  
Spectroscopic Characterization ◽  
Biological Processes ◽  
X Ray Diffraction ◽  
Electron Nuclear Double Resonance ◽  
X Ray ◽  
High Valent ◽  
X Ray Absorption ◽  
Structure Calculations

High-valent iron species are key intermediates in oxidative biological processes, but hexavalent complexes apart from the ferrate ion are exceedingly rare. Here, we report the synthesis and structural and spectroscopic characterization of a stable Fe(VI) complex (3) prepared by facile one-electron oxidation of an Fe(V) bis(imido) (2). Single-crystal x-ray diffraction of 2 and 3 revealed four-coordinate Fe centers with an unusual “seesaw” geometry. 57Fe Mössbauer, x-ray photoelectron, x-ray absorption, and electron-nuclear double resonance (ENDOR) spectroscopies, supported by electronic structure calculations, support a low-spin (S = 1/2) d3 Fe(V) configuration in 2 and a diamagnetic (S = 0) d2 Fe(VI) configuration in 3. Their shared seesaw geometry is electronically dictated by a balance of Fe-imido σ- and π-bonding interactions.

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