查看完整版本: 小角度X射线衍射（散射）技术应用资源集锦

小角度X射线衍射（散射）技术应用资源集锦

[size=4][color=Blue]最近看的不是会员对小角度X射线散射技术的应用比较关心，所以有必要将这些技术简要的说明，并且把这方便的资源汇总一些，如果有资源请大家跟贴附上，主要资源包括（我自己想的）：[/color]
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[b][color=Green]小角度xrd技术与仪器

小角度xrd主要应用（文章等）

小角度xrd技术（学术）报告[/color][/b]

[b][color=Red]欢迎大家积极参与[/color][/b][/size]:handshakeshake" />shake" /> :time: :hot11" />1" />
[quote]
[align=center][size=4][color=DarkGreen][b] Small Angle X-Ray Scattering (SAXS)[/b][/color][/size]
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[b]Small Angle X-ray Scattering [/b](SAXS) [color=Red]enables to measure structural features on length scales between 1 nm up to several hundred of nanometers by analyzing the scattering pattern at very low angles from the direct X-ray beam. The technique is used in various applications to get access to different parameters such as polymer’s molecular mass and supramolecular structure, pore’s size distribution and shapes in colloids[/color].

Depending on the requirements on intensity and resolution, different system configurations can be used. Compact 1-dimensional SAXS systems with line focus sealed tubes coupled to 1D multilayer optics are highly efficient and cost effective solutions for isotropic samples analysis. Anisotropic samples are best characterized with 2-dimensional SAXS systems using 2 or 3 pinhole collimation and integrating 2D multilayer optics. The scale of observable features depends strongly on the quality of the beam irradiating the sample and typically a collimated or slightly focusing monochromatic beam is used to achieve high intensity at high resolutions (low scattering angles or high length scales in the real space).

FOX optics are recognized as a very efficient and cost effective solution for upgrading SAXS installations. It enables to achieve very low values of qmin (minimum scattering vector) while providing high flux to the sample and low background. Our optics are adapted to all standard set-up including rotating anodes and sealed tubes (point or line sources) installations. Moreover, Xenocs can provide a complete beam delivery system including the collimation design support in order to achieve the best upgrade for your installation.
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Small angle X-ray diffraction (SAXS) is one of the most useful techniques for structural investigation of solid polymers. In particular, SAXS can provide [color=Red]information about morphological features such as void size, crazing, component segregation in copolymers and lamellar structure of crystalline polymers [/color][1, 2 and 3].

[b][i]The use of synchrotron radiation has opened new possibilities to these X-ray studies[/i][/b]. The radiation produced in electron or positron storage rings allows to obtain monochromatic beams far more intense than conventional X-ray sources [4 and 5]. For this reason, it is possible to record SAXS patterns in very short times and to follow, in real time, the structural changes occurring during crystallization, melting and processing of polymers [6, 7 and 8].

On the other hand, SAXS techniques have also proved to be very useful in the study of polymer blends [9, 10, 11, 12, 13, 14, 15, 16 and 17]. Particularly, these techniques can give [color=Red]information about the morphology [9 and 13], phase separation [15] and interlamellar, interfibrillar or interspherulitic placement of the non-crystallizable component [/color][10, 16 and 17].

[b]References[/b]
1. F.J. Balta Calleja and C.G. Vonk. X-ray scattering of synthetic polymers Elsevier, Amsterdam (1989).

2. A. Guinier and G. Fournet. Small angle scattering of X-ray Wiley (Chapman and Hall), New York (London) (1955).

3. O. Glatter and O. Kratky. Small angle X-ray scattering Academic Press, New York (1982).

4. G. Elsner, C. Riekel and H.G. Zachmann. Adv Polym Sci 67 (1985), p. 1. Full Text via CrossRef

5. S.J. Spells. Characterization of solid polymers Chapman and Hall, London (1994) p. 3, 56.

6. H.G. Zachmann. Nucl Instrum Methods Phys Res 97 (1995), p. 209. Abstract | PDF (738 K)

7. K.N. Krüger and H.G. Zachmann. Macromolecules 26 (1993), p. 5202. View Record in Scopus | Cited By in Scopus (87)

8. M. Bark and H.G. Zachmann. Acta Polymer 44 (1993), p. 259. Full Text via CrossRef

9. J.S. Lin, E.Y. Sheu and Y.H.R. Jois. J Appl Polym Sci 55 (1995), p. 655. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (2)

10. C.H. Lee, T. Okada, H. Saito and T. Inoue. Polymer 38 (1997), p. 31. SummaryPlus | Full Text + Links | PDF (268 K) | View Record in Scopus | Cited By in Scopus (9)

11. W.C. Zin and R.J. Roe. Macromolecules 17 (1984), p. 183. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (41)

12. Y.Y. Cheng, M. Brillhart, P. Cebe and M. Capel. J Polym Sci Polym Phys 34 (1996), p. 2953. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (15)

13. S. Rabiej, A. Wlochowicz, J. Janicki and M. Bryjak. Acta Polymerica 37 (1986), p. 286. Full Text via CrossRef

14. B.K. Annis, G.D. Wignall, A.R. Hopkins, P.G. Rasmussen and R.A. Basheer. J Polym Sci Polym Phys 35 (1997), p. 2765. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (7)

15. Y. Li and B.J. Jungnickel. Polymer 34 (1993), p. 9. Abstract | View Record in Scopus | Cited By in Scopus (52)

16. P. Huo and P. Cebe. Macromolecules 26 (1993), p. 3127. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (40)
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[quote]
[size=5]Small-angle X-ray scattering[/size]
[color=Blue]From Wikipedia, the free encyclopedia[/color]


[b]Small-angle X-ray scattering [/b](SAXS) is a [b]small-angle scattering[/b] (SAS) technique where the[color=Red] elastic scattering of X-rays (wavelength 0.1 ... 0.2 nm) by a sample which has inhomogeneities in the nm-range, is recorded at very low angles (typically 0.1 - 10°). In this angular range, information about the shape and size of macromolecules, characteristic distances of partially ordered materials, pore sizes and the like is contained. SAXS is capable of delivering structural information of macromolecules between 5 and 25 nm, of repeat distances in partially ordered systems of up to 150 nm. USAXS (ultra-small angle X-ray scattering) can resolve even larger dimensions.[/color]

The advantage over crystallography is that the samples need not be crystalline, the measurement is non-destructive and NMR methods encounter problems with macromolecules of higher molecular mass (> 30000-40000). However, owing to the random orientation of dissolved or partially ordered molecules there occurs spatial averaging which leads to a loss of information.



    *[b] 1 Applications[/b]
[b]    * 2 SAXS instruments[/b]
[b]    * 3 Porod's law[/b]
[b]    * 4 See also[/b]
[b]    * 5 External links and references[/b]

[b]*** Applications[/b]

SAXS is used for the determination of the microscale or nanoscale structure of particle systems in terms of such parameters as averaged particle sizes, shapes, distribution, and surface-to-volume ratio. The materials can be solid or liquid and they can contain solid, liquid or gaseous domains (so-called particles) of the same or another material in any combination. The method is accurate, non-destructive and usually requires only a minimum of sample preparation. Applications are very broad and include colloids of all types, metals, cement, oil, polymers, plastics, proteins, foods and pharmaceuticals and can be found in research as well as in quality control. The X-ray source can be a laboratory source or Synchrotron light which provides a higher X-ray flux.

[b] ***SAXS instruments[/b]

The major problem that must be overcome in SAXS instrumentation is the separation of the weak scattered intensity form the strong main beam. The smaller the desired angle, the more difficult this becomes. The problem is comparable to one encountered when trying to observe a weakly radiant object close to the sun, like the sun's corona. Only if the moon blocks out the main light source does the corona become visible. Likewise, in SAXS the main beam must be blocked after its interaction with the sample, without blocking the closely adjacent scattered radiation. Most available X-ray sources produce divergent beams and this compounds the problem. In principle the problem could be overcome by focussing the main beam, but this is not easy when dealing with X-rays, because lenses are virtually non-existent. This is why most practical small angle devices must rely on collimation instead.

[color=Green]SAXS instruments can be divided into two main groups: point-collimation and line-collimation instruments:[/color]

1) point-collimation instruments have pinholes that shape the X-ray beam to a small circular or elliptical spot that illuminates the sample. Thus the scattering is centro-symmetrically distributed around the primary X-ray beam and the scattering pattern in the detection plane consists of circles around the primary beam. Owing to the small illuminated sample volume and the wastefulness of the collimation process -only those photons are allowed to pass that happen to fly in the right direction- the scattered intensity is small and therefore the measurement time is in the order of hours or days. Point-collimation allows to determine the orientation of non-isotropic systems (fibres, sheared liquids).

2) line-collimation instruments confine the beam only in one dimension so that the beam profile is a long but narrow line. The illuminated sample volume is much larger compared to point-collimation and the scattered intensity at the same flux density is proportionally larger. Thus measuring times with line-collimation SAXS instruments are much shorter compared to point-collimation and are in the range of minutes to hours. This disadvantage is that the recorded pattern is essentially an integrated superposition (a self-convolution) of many pinhole adjacent pinhole patterns. The resulting smearing can be removed using deconvolution methods based on Fourier transformation, but only if the system is isotropic.

[b]*** Porod's law[/b]

SAXS patterns are typically represented as scattered intensity as a function of the scattering vector q=4π.sin(θ)/λ. One interpretation of this vector is that of a resolution or yardstick with which the sample is observed. In the case two-phase sample, e.g. small particles in liquid suspension, the only contrast leading to scattering in the typical range of resolution of the SAXS is simply, Δρ the difference in average electron density between the particle and the surrounding liquid, because variations in ρ due to the atomic structure only become visible at higher angles in the WAXS regime. This means that the total integrated intensity of the SAXS pattern (in 3D) is an invariant quantity proportional to the square Δρ². In 1D projection, as usually recorded for a isotropic pattern this invariant = ʃI(q).q2.dq, where the integral runs from q=0 to wherever the SAXS pattern is assumed to end and the WAXS pattern starts. It is also assumed that the density does not vary in the liquid or inside the particles, i.e. there is binary contrast.

In the transitional range at the high resolution end of the SAXS pattern the only contribution to the scattering come from the interface between the two phases and the intensity should drop with the fourth power of q if this interface is smooth. This a consequence of the fact that in this regime any other structural features, e.g. interference between one surface of a particle and the one on the opposite side, are so random that they do not contribute. This is known as Porod's law:

        limq->high I = S.q-4

This allows the surface area S of the particles to be determined for SAXS. However, since the advent of fractal mathematics it has become clear that this law requires adaptation because the value of the surface S may itself be a function of the yardstick by which it is measured. In the case of a fractally rough surface area with a dimensionality d between 2-3 Porod's law becomes:

        limq->high I = S'.q-(6-d)

Thus if plotted logarithmically the slope of ln(I) versus ln(q) would vary between -4 and -3. Slopes less negative than -3 are also possible in fractal theory but require a volume fractal rather than a surface fractal and in a sense that would represent a single phase system (e.g. a solution with polymer molecules in it) rahter than a two phase system.
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网络资源汇集（网站收集）

[list][*]:hand  [url=http://coecs.ou.edu/Brian.P.Grady/saxs.html]Small-Angle X-Ray Scattering, [img]http://coecs.ou.edu/Brian.P.Grady/images/sw_top.gif[/img][/url][/list]

[[i] 本帖最后由 nano 于 2007-12-16 08:24 编辑 [/i]]

学术报告集

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上传之中，请稍候:lol
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[[i] 本帖最后由 nano 于 2007-12-16 08:31 编辑 [/i]]

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SMALL ANGLE XRAY SCATTERING (SAXS)

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X-ray diffraction by thin films and nanostructures:Introduction and Review

[size=4][b]X-ray diffraction by thin films and nanostructures:Introduction and Review[/b][/size]
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[[i] 本帖最后由 nano 于 2007-12-16 09:43 编辑 [/i]]

Great job! Thanks a lot for sharing the information! :good

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thanks for sharing

非常感谢！！:readrules :hot1 :good1

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谢谢分享！:handshake

Thanks for your sharing1

多谢分享，正需要这方面

正好我要做关于这方面的，太好了！

thanks for sharing

学习一下:handshake :handshake

thanks for sharing

good topic. :good1 :good1 :good1 :good1 :good1