Comparison of the Structures of Stretched Linear Polymers

1945 ◽  
Vol 18 (4) ◽  
pp. 763-771
Author(s):  
Maurice L. Huggins
Keyword(s):  
Polyvinyl Alcohol ◽  
Polyvinyl Chloride ◽  
Linear Polymers ◽  
Interatomic Distances ◽  
Polyvinylidene Chloride ◽  
X Ray

Abstract Published x-ray data from crystalline selenium and tellurium and from stretched sulfur (amorphous), polyethylene, polyisobutylene, polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, polyoxymethylene, polyoxyethylene, polyethylene disulfide, polyethylene tetrasulfide, and polyphosphonitrile chloride are compared. In most cases the experimental identity-distance in the direction of the chain axes and the expected interatomic distances and interbond angles are found to be in agreement with the assumption that the chain atoms form a regular spiral, unidirectional in each chain and of uniform pitch. Apparent exceptions are briefly discussed.

Some Aspects of Exelfs Analysis in the Electron Microscope

1980 ◽  
Vol 38 ◽  
pp. 118-119
Author(s):  
D. E. Johnson ◽  
S. Csillag
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Energy Loss ◽  
Analytical Electron Microscopy ◽  
Interference Effects ◽  
Interatomic Distances ◽  
X Ray ◽  
Structure Information ◽  
Microanalytical Technique ◽  
Analytical Electron

Recently, the applications area of analytical electron microscopy has been extended to include the study of Extended Energy Loss Fine Structure (EXELFS). Modulations past an ionization edge in the energy loss spectrum (EXELFS), contain atomic fine structure information similar to Extended X-ray Absorbtion Fine Structure (EXAFS). At low momentum transfer the main contribution to these modulations comes from interference effects between the outgoing excited inner shell electron waves and electron waves backscattered from the surrounding atoms. The ability to obtain atomic fine structure information (such as interatomic distances) combined with the spatial resolution of an electron microscope is unique and makes EXELFS an important microanalytical technique.

Effect of nanofibrous porosity on the X-ray attenuation properties of electrospun n-Bi2O3/epoxy–polyvinyl alcohol (PVA) nanofiber mats

2018 ◽  
Vol 124 (8) ◽  
Author(s):  
Bassam M. Abunahel ◽  
Ramzun Maizan Ramli ◽  
Khetam M. Quffa ◽  
Nurul Zahirah Noor Azman
Keyword(s):  
Polyvinyl Alcohol ◽  
X Ray ◽  
Nanofiber Mats

Investigations of Actinide Metals and Compounds under Pressure Provide Important Insights into Bonding and Chemistry

2003 ◽  
Vol 802 ◽  
Author(s):  
R. G. Haire ◽  
S. Heathman ◽  
T. Le Bihan ◽  
A. Lindbaum ◽  
M. Iridi
Keyword(s):  
Structural Changes ◽  
Chemical Properties ◽  
X Ray Diffraction ◽  
Interatomic Distances ◽  
X Ray ◽  
Effect Of Pressure ◽  
Electronic Configurations ◽  
5F Electrons ◽  
Actinide Series ◽  
Alloys And Compounds

ABSTRACTOne effect of pressure on elements and compounds is to decease their interatomic distances, which can bring about dramatic perturbations in their electronic nature and bonding, which can be reflected in changes in physical and/or chemical properties. One important issue in the actinide series of elements is the effect of pressure on the 5f-electrons. We have probed changes in electronic behavior with pressure by monitoring structure by X-ray diffraction, and have studied several actinide metals and compounds from thorium through einsteinium. These studies have employed angle dispersive diffraction using synchrotron radiation, and energy dispersive techniques via conventional X-ray sources. The 5f-electrons of actinide metals and their alloys are often affected significantly by pressure, while with compounds, the structural changes are often not linked to the involvement of 5 f-electron. We shall present some of our more recent findings from studies of selected actinide metals, alloys and compounds under pressure. A discussion of the results in terms of the changes in electronic configurations and bonding with regard to the element's position in the series is also addressed.

Preparation and Characterization of Ni2+-Montmorillonite/Polyvinyl Alcohol Water-Soluble Nanocomposite Film

2005 ◽  
Vol 13 (8) ◽  
pp. 839-846 ◽  
Author(s):  
Li-Ping Wang ◽  
Yun-Pu Wang ◽  
Fa-Ai Zhang
Keyword(s):  
Polyvinyl Alcohol ◽  
Photoelectron Spectroscopy ◽  
Thermal Characteristics ◽  
Water Soluble ◽  
Scanning Calorimetry ◽  
Xps Spectra ◽  
X Ray ◽  
Alcohol Water ◽  
Ft Ir ◽  
Silicate Layers

A new type of nano-composite film was prepared from polyvinyl alcohol, Ni2+-montmorillonite (Ni2+-MMT), defoamer, a levelling agent and a plasticizer. Its thermal characteristics were studied by Differential Scanning Calorimetry (DSC). The intermolecular interactions were measured by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS), and the tensile strength (TS) and elongation at break (%E) were measured. The microstructures were studied by X-ray diffraction (XRD) and atomic force microscopy (AFM). FT-IR and XPS spectra indicated that cross-linking has taken place between PVA and Ni2+-MMT. XRD and AFM indicate that the PVA molecules had inserted themselves into the silicate layers of MMT, exfoliating them and dispersing them randomly into the PVA matrix. Compared to pure PVA film, the TS of the films was increased and %E decreased when the Ni2+-Montmorillonite was added and the dissolution temperature of the film was also reduced.

Inorganic crystal structures from powder data—A retrospection

1999 ◽  
Vol 14 (1) ◽  
pp. 5-9 ◽  
Author(s):  
L’ubomír Smrčok ◽  
Ján Mailing
Keyword(s):  
Short Review ◽  
Powder Diffraction Data ◽  
Interatomic Distances ◽  
X Ray ◽  
Space Groups ◽  
Neutron Powder Diffraction Data ◽  
Inorganic Crystal ◽  
Reported Data ◽  
Atomic Coordinates ◽  
Icsd Database

More than 10 000 inorganic structures based on both X-ray and neutron powder diffraction data were extracted from the ICSD database and analyzed considering overall trends, cell symmetries, occurrence of the space groups, complexity, precision and reliability of reported data. It was found that the major amount of structures belong to higher symmetries and have 2–5 atoms in the asymmetric unit. Less than 35% of the e.s.d.'s of atomic coordinates is ≤10−3 and 10−4 or better was reached in only 5% of cases. Approximately one-quarter of papers contain possibly inaccurate atomic coordinates or interatomic distances. A short review of journals publishing structures derived from powders is also given.

X-Ray Absorption Spectroscopic Studies of Catalytic Materials

1988 ◽  
Vol 143 ◽  
Author(s):  
G. H. Via ◽  
J. H. Sinfelt ◽  
G. Meitzner ◽  
F. W. Lytle
Keyword(s):  
Fine Structure ◽  
Physical Environment ◽  
Bimetallic Catalysts ◽  
Spectroscopic Studies ◽  
Interatomic Distances ◽  
X Ray ◽  
Coordination Numbers ◽  
Supported Platinum ◽  
High Fraction ◽  
X Ray Absorption

AbstractX-ray absorption spectra (XAS) contain information in the LIII near-edge region on filling of the absorber d-band, and in the extended fine-structure region on the physical environment of the absorber. We report here an evaluation of the effect on platinum LIII edges of preparation in clusters with a high fraction of Pt atoms at the surface. We also report the effects on platinum and rhenium LIII edges from addition of copper. These effects are surprisingly small.We have also re-evaluated extended x-ray absorption fine-structure spectra (EXAFS) of platinum and rhenium in alumina-supported platinum-rhenium bimetallic catalysts. A novel feature of this new analysis was the requirement that interatomic distances, coordination numbers, and Debye-Waller type factors maintain certain physically necessary relationships among themselves. This procedure decreased the number of free variables and increased the amount of information returned by the analysis.

On the effect of Ga and In substitutions in the Ca11Bi10and Yb11Bi10bismuthides crystallizing in the tetragonal Ho11Ge10structure type

2018 ◽  
Vol 74 (3) ◽  
pp. 269-273 ◽  
Author(s):  
Alexander Ovchinnikov ◽  
Svilen Bobev
Keyword(s):  
Bond Length ◽  
Length Distribution ◽  
Structural Response ◽  
Structure Type ◽  
First Principle ◽  
X Ray Diffraction ◽  
Interatomic Distances ◽  
X Ray ◽  
Type Bond ◽  
Bond Length Distribution

The Ga- and In-substituted bismuthides Ca11GaxBi10–x, Ca11InxBi10–x, Yb11GaxBi10–x, and Yb11InxBi10–x(x< 2) can be readily synthesized employing molten Ga or In metals as fluxes. They crystallize in the tetragonal space groupI4/mmmand adopt the Ho11Ge10structure type (Pearson codetI84; Wyckoff sequencen2m j h2e2d). The structural response to the substitution of Bi with smaller and electron-poorer In or Ga has been studied by single-crystal X-ray diffraction methods for the case of Ca11InxBi10–x[x= 1.73 (2); octabismuth undecacalcium diindium]. The refinements show that the In atoms substitute Bi only at the 8hsite. The refined interatomic distances show an unconventional – for this structure type – bond-length distribution within the anionic sublattice. The latter can be viewed as consisting of isolated Bi3−anions and [In4Bi820−] clusters for the idealized Ca11In2Bi8model. Formal electron counting and first-principle calculations show that the peculiar bonding in this compound drives the system toward an electron-precise state, thereby stabilizing the observed bond-length pattern.

scholarly journals What the presence of regulated chemical elements in beached lacustrine plastics can tell us: the case of Swiss lakes

2021 ◽  
Vol 193 (11) ◽  
Author(s):  
Montserrat Filella ◽  
Juan-Carlos Rodríguez-Murillo ◽  
Andrew Turner
Keyword(s):  
Polyvinyl Chloride ◽  
Flame Retardants ◽  
Chemical Elements ◽  
Fluorescence Spectrometry ◽  
Lake Geneva ◽  
Plastic Pollution ◽  
X Ray ◽  
Management Schemes ◽  
Standing Stocks ◽  
Insight Into

AbstractPlastics (n = 3880) have been sampled from 39 beaches of ten Swiss lakes of varying sizes, hydrodynamics, and catchments, with a selection (n = 598) analysed for potentially hazardous (and regulated) chemical elements (As, Ba, Br, Cd, Cr, Hg, Pb, Sb, Se) by X-ray fluorescence spectrometry. Plastic objects and fragments with identifiable or unidentifiable origins were present on all beaches surveyed, and were often most abundant in proximity to major riverine inputs. Chemical elements were detected in between two (Hg) and 340 (Ba) samples with maximum concentrations exceeding 2% by weight for Ba, Cd, Cr, Pb, and Sb. Inter-element relationships and characteristics of the samples suggest that elements are largely present as various additives, including pigments (e.g., Cd2SSe, PbCrO4), stabilizers (in polyvinyl chloride), and flame retardants (Br). Observations are similar to, and complement, those previously reported in Switzerland’s largest lake (Lake Geneva). Comparison of concentrations of targeted chemical elements in beached plastic with currently used plastics illustrate the interest of these types of measurements in providing an insight into the persistence of plastics in standing stocks and in lakes. This information could help to introduce management schemes that consider whether plastic pollution is new or old and act accordingly.

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