Small Angle X-Ray Scattering (Saxs) and IR Study of Microvoid Dynamics in Annealed RF Sputter-Deposited A-SI:H

1992 ◽  
Vol 258 ◽  
Author(s):  
H. Jia ◽  
J. Shinar ◽  
Y. Chen ◽  
D. L. Williamson
Keyword(s):  
Small Angle ◽  
Volume Fraction ◽  
Rf Sputtering ◽  
The Other ◽  
Columnar Microstructure ◽  
Saxs Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Sputter Deposited ◽  
Ir Study

ABSTRACTA SAXS and IR study of microvoid distribution and dynamics in a-Si:H deposited by rf sputtering at 200 – 600 W on nominally unheated substrates is described and discussed. The 640 cm-1 band of the 200 W film yielded a total Si-bonded H content CH=21 at. %; the 840 – 890 cm-1 band yielded a dihydride content CH2 3.4 at. %. The SAXS measurements yielded a microvoid volume fraction vf=8.2 vol.%, and tilting SAXS data indicated elongated voids consistent with a columnar microstructure. In the other films, 9<CH<12 at. % and CH2 was negligible, vf was -2 vol. %. Annealing from 250°C to 310°C for 6 hrs resulted basically in no changes of CH and vf. However CH decreased and vf increased significantly after annealing at 350°C and above. The results showed a strong correlation between the IR determined CH and CH2 and the SAXS determined vf.

An improved small-angle X-ray scattering analysis of δ′ precipitation in an Al–Li alloy for growth kinetic studies

1999 ◽  
Vol 32 (3) ◽  
pp. 426-435 ◽  
Author(s):  
Cheng-Si Tsao ◽  
Tsang-Lang Lin
Keyword(s):  
Particle Size ◽  
Size Distribution ◽  
Hard Sphere ◽  
Volume Fraction ◽  
The Other ◽  
Improved Method ◽  
Saxs Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Two Parameters

An improved method for small-angle X-ray scattering (SAXS) data analysis is developed to reconstruct the free-form particle size distribution of δ′ precipitation in an Al–Li alloy. This improved method consists of four iterative steps; the interparticle interference is also included. The indirect transform method (ITM) plus a hard-sphere (HS) model which considers the depleted zones are used in the analysis of δ′ precipitation in an Al–Li alloy. Two parameters, namely the hard-sphere volume fraction, ηHS, and the ratio of hard-sphere radius to the particle radius,RHS/R, which determine the structure factor of the interparticle effect, are iteratively calculated using the monodisperse assumption and Gaussian size distribution. These two parameters are finally used in reconstructing the particle size distribution by the ITM + HS method. This method is tested by analysing simulated SAXS data and shows a better agreement than found in similar studies. This improved method is applied to analyse a set of experimental SAXS intensities from δ′ (Al3Li particles) precipitation in an Al–9.7 at.% Li alloy. The monodisperse results are compared with the polydisperse ITM + HS results. The current ITM + HS method fits the SAXS data better than the other methods. The variations of average radii with aging time were found to follow the kinetic power law. The SAXS results are used to investigate the theoretical kinetic model of the volume-fraction effect on late-stage coarsening (Ostwald ripening). By comparing both experimentally obtained asymptotic size distributions of δ′ particles as well as coarsening rate constants with those predicted by the various kinetic models, the modified Lifshitz–Slyozov–Wagner (MLSW) theory is found to be in better agreement with the experimental results than the other theories.

Structural refinement by restrained molecular-dynamics algorithm with small-angle X-ray scattering constraints for a biomolecule

2004 ◽  
Vol 37 (1) ◽  
pp. 103-109 ◽  
Author(s):  
Masaki Kojima ◽  
Alexander A. Timchenko ◽  
Junichi Higo ◽  
Kazuki Ito ◽  
Hiroshi Kihara ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Molecular Dynamics ◽  
Small Angle ◽  
Protein Structures ◽  
Saxs Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Saxs Curve ◽  
Restrained Molecular Dynamics ◽  
Ray Scattering

A new algorithm to refine protein structures in solution from small-angle X-ray scattering (SAXS) data was developed based on restrained molecular dynamics (MD). In the method, the sum of squared differences between calculated and observed SAXS intensities was used as a constraint energy function, and the calculation was started from given atomic coordinates, such as those of the crystal. In order to reduce the contribution of the hydration effect to the deviation from the experimental (objective) curve during the dynamics, and purely as an estimate of the efficiency of the algorithm, the calculation was first performed assuming the SAXS curve corresponding to the crystal structure as the objective curve. Next, the calculation was carried out with `real' experimental data, which yielded a structure that satisfied the experimental SAXS curve well. The SAXS data for ribonuclease T1, a single-chain globular protein, were used for the calculation, along with its crystal structure. The results showed that the present algorithm was very effective in the refinement and adjustment of the initial structure so that it could satisfy the objective SAXS data.

Analysis of the small-angle intensity scattered by a porous and granular medium

2003 ◽  
Vol 36 (2) ◽  
pp. 338-347 ◽  
Author(s):  
O. Spalla ◽  
S. Lyonnard ◽  
F. Testard
Keyword(s):  
Small Angle ◽  
Granular Medium ◽  
Unit Volume ◽  
Large Range ◽  
Volume Fraction ◽  
Complete Analysis ◽  
X Ray ◽  
X Ray Scattering ◽  
Pore Volume Fraction ◽  
Porous Grains

Using X-ray scattering over a large range of scattering vectors, it is shown how to measure both the pore volume fraction and pore specific surface of an assembly of porous grains forming a powder. Depending on the presence or not of solvent in the inner pores and in the intergranular media, the scattered signal per unit volume of solid or per unit volume of grain are introduced, which allow a complete analysis even when the thickness of the layer and its compactness are unknown. The method is applied to three different systems presenting a well defined Porod regime at large scattering vector.

Quality control of protein standards for molecular mass determinations by small-angle X-ray scattering

2010 ◽  
Vol 43 (2) ◽  
pp. 237-243 ◽  
Author(s):  
Shuji Akiyama
Keyword(s):  
Quality Control ◽  
Molecular Mass ◽  
Small Angle ◽  
Biological Macromolecules ◽  
Average Deviation ◽  
Saxs Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Standard Quality ◽  
Ray Scattering

Small-angle X-ray scattering (SAXS) is a powerful technique with which to evaluate the size and shape of biological macromolecules in solution. Forward scattering intensity normalized relative to the particle concentration,I(0)/c, is useful as a good measure of molecular mass. A general method for deducing the molecular mass from SAXS data is to determine the ratio ofI(0)/cof a target protein to that of a standard protein with known molecular mass. The accuracy of this interprotein calibration is affected considerably by the monodispersity of the prepared standard, as well as by the precision in estimating its concentration. In the present study, chromatographic fractionation followed by hydrodynamic characterization is proposed as an effective procedure by which to prepare a series of monodispersed protein standards. The estimation of molecular mass within an average deviation of 8% is demonstrated using monodispersed bovine serum albumin as a standard. The present results demonstrate the importance of protein standard quality control in order to take full advantage of interprotein calibration.

scholarly journals Structural Study of the Photo-Mediated Growth of Silver Nanoprisms

Molecules ◽  
2020 ◽  
Vol 25 (22) ◽  
pp. 5413
Author(s):  
Matti Knaapila ◽  
Ulla Vainio ◽  
Sophie E. Canton ◽  
Gunnel Karlsson
Keyword(s):  
Particle Size ◽  
Small Angle ◽  
Volume Ratio ◽  
Direct Methods ◽  
Saxs Data ◽  
Aqueous Dispersions ◽  
X Ray ◽  
Silver Nanoprisms ◽  
X Ray Scattering ◽  
Ag Particles

We present a small-angle X-ray scattering (SAXS) study of the anisotropic photoinduced growth of silver (Ag) nanoprisms in aqueous dispersions. The growth of nearly spherical (<10 nm) Ag particles into large (>40 nm) and thin (<10 nm) triangular nanoprisms induced by 550 nm laser is followed in terms of particle size using indirect and direct methods for irradiation times up to 150 min. During the process, the surface-to-volume ratio of the particles decreased. The SAXS data of the initial solution fit well to the model of polydisperse spheres with pronounced average diameters around 7.4 nm and 10 nm. The data after 45 min irradiation fit well to the model containing approximately the same amount of the initial particles and the end product, the nanoprisms.

scholarly journals Characterization of Crystal Microstructure Based on Small Angle X-ray Scattering (SAXS) Technique

Molecules ◽  
2020 ◽  
Vol 25 (3) ◽  
pp. 443 ◽  
Author(s):  
Hongfan Wang ◽  
Jinjiang Xu ◽  
Shanhu Sun ◽  
Yanru Liu ◽  
Chunhua Zhu ◽  
...  
Keyword(s):  
Small Angle ◽  
Volume Fraction ◽  
Surface Effect ◽  
Crystal Surface ◽  
Particle Density ◽  
Test Results ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

Small-angle X-ray scattering (SAXS) is an effective method to obtain microstructural information of materials. However, due to the influence of crystal surface effects, SAXS has a deviation in the characterization of the crystal microstructure. In order to solve the influence of crystal surface effect on the internal defect signal, the microstructure of Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) crystal was characterized by soaking the sample in the matching solution. We found that the absolute scattering intensity, specific surface and volume fraction of the sample in the matching solution are significantly lower than the initial sample, which solves the influence of the crystal surface effect on the test results. Comparing the scattering results of the samples in different electron density matching solutions, it was found that the best result was obtained when using GPL-107 perfluoropolyether (PFPE) matching solution and the same law was obtained by controlling the experiment with 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (CL-20) crystal. The fitting density was calculated according to the theoretical density and void volume fraction of the sample, and the calculated results are close to the test results of Particle Density Distribution Analyzer (PDDA). Based on this paper, we provide a method to obtain the correct information of crystal microstructure.

Small-Angle X-Ray Scattering for the Discerning Macromolecular Crystallographer

2014 ◽  
Vol 67 (12) ◽  
pp. 1786 ◽  
Author(s):  
Lachlan W. Casey ◽  
Alan E. Mark ◽  
Bostjan Kobe
Keyword(s):  
Structural Biology ◽  
Small Angle ◽  
Significant Risk ◽  
Macromolecular Crystallography ◽  
Saxs Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

The role of small-angle X-ray scattering (SAXS) in structural biology is now well established, and its usefulness in combination with macromolecular crystallography is clear. However, the highly averaged SAXS data present a significant risk of over-interpretation to the unwary practitioner, and it can be challenging to frame SAXS results in a manner that maximises the reliability of the conclusions drawn. In this review, a series of recent examples are used to illustrate both the challenges for interpretation and approaches through which these can be overcome.

Influence of polychromaticity on particle structure determination in small-angle X-ray scattering

2015 ◽  
Vol 48 (6) ◽  
pp. 1935-1942 ◽  
Author(s):  
Wenjia Wang ◽  
Eleonora V. Shtykova ◽  
Vladimir V. Volkov ◽  
Guangcai Chang ◽  
Lianhui Zhang ◽  
...  
Keyword(s):  
Small Angle ◽  
Structural Parameters ◽  
Shape Reconstruction ◽  
The Body ◽  
Particle Structure ◽  
Saxs Data ◽  
Time Resolved ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

Pink beams are now widely used for small-angle X-ray scattering (SAXS) data collection owing to their high intensity. However, the wavelength spread of a pink beam is a factor of 100 higher than that of a monochromatic beam, thus causing the experimental data to be smeared. To reveal the influence of polychromaticity on shape reconstruction, four geometric bodies (sphere, cube, helix and long cylinder) were used for SAXS data analysis. The results reveal that the influence of polychromaticity on the process of shape reconstruction is significantly more dependent on the geometry of the body than on its size. Scattering objects with smoothed scattering curves can tolerate a higher wavelength spread than those with tortuous curves. It is further demonstrated that the structural parameters calculated from the smeared data sets have little deviation from the ideal ones, which indicates the possibility of using a light source with a greater wavelength spread than a conventional pink beam for special time-resolved SAXS experiments. Finally, it is concluded that SAXS data collected in pink-beam mode can be used directly for structural calculations and model reconstructions without a desmearing procedure.

Silicon photodiode detector for small-angle X-ray scattering

1990 ◽  
Vol 23 (5) ◽  
pp. 430-432 ◽  
Author(s):  
P. R. Jemian ◽  
G. G. Long
Keyword(s):  
Small Angle ◽  
Signal To Noise Ratio ◽  
Scintillation Counter ◽  
Detector Response ◽  
Silicon Photodiode ◽  
Double Crystal ◽  
Saxs Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

A photodiode X-ray detector was built to measure small-angle X-ray scattering (SAXS) at a synchrotron-radiation source in conjunction with a double-crystal diffractometer SAXS camera at photon energies between 5 and 11 keV. The photodiode detector response in this energy range is linear at photon counting rates up to 1012 photons s−1 and thus it was not necessary to attenuate the monochromatic X-ray beam with calibrated foils. SAXS data taken with a scintillation counter and the photodiode detector are compared, demonstrating marked improvement in counting statistics, rate of data acquisition and signal-to-noise ratio.

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