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Scattering Instrument Design/Development: Current Funding Sources, State of Ohio, OBR Equipment Grant (Our part $250,000) Sandia National Labs, Å $500,000 in equipment donations to UC.
Students Involved: Sathish Sukumaran, PhD Candidate.
SukumaSH@email.uc.edu
Shrish Rane, PhD Candidate
ranesy@email.uc.edu
Scattering Instrument Design/Development: Current Funding Sources, State of Ohio, OBR Equipment Grant (Our part $250,000) Sandia National Labs, Å $500,000 in equipment donations to UC.
I1. "Tacticity effects on polymer blend miscibility", Beaucage, G.; Stein, R. S.; Hashimoto, T.; Hasegawa, H., Macromolecules (1991), 24(11), 3443-8.
I2. "From small angle x-ray scattering to reflectivity: instrumentation and sample study", Hua, D. W.; Beaucage, G.; Kent, M. S., J. Mater. Res. (1996), 11(2), 273-6.
Instrument development and support is a critical feature of our research program. At UMass [I1] a new instrument for SALS was developed which used a projected scattering image on a screen that was imaged using a macro-lens and a semi-conductor OMA camera. This design was very successful in studying wide angle scattering for spinodal decomposition in polymer blends. It is also an extremely flexible instrument and a write-up of the instrument was included in the first manuscript on the i-PVME/PS system [I1]. This design was copied in an instrument built at Sandia and transferred to UC which uses a 2-D CCD optical camera. SANS and SAXS work at UMass was done mostly at national user facilities at Argonne, Los Alamos, NIST and Brookhaven.
At Sandia, a scattering center based on two rotating anode generators was developed. This facility includes a pinhole camera, Kratky camera, Bonse-Hart camera and an Inel 120¡ wire detector based XRD camera equipped with a high temperature stage. A detailed description of this facility is available on the Web at:
http://www.sandia.gov/materials/sciences/Capabilities/Scattering/Scattering_Capabilities.html .
An x-ray reflectometer was also built based on the Kratky camera and designed so that the Kratky would be available as a dual use instrument [I2]. Development of this lab was a collaborative effort between a number of workers including D. W. Hua, now at SCM Chemicals in Baltimore, T. Rieker who remains as lab manager at Sandia and Al Hurd, Paul Schmidt and Dale Schaefer as project managers.
At UC we have setup a Bonse-Hart camera, a Kratky camera and a Phillips diffractometer. These operate on a 12kW Rigaku rotating anode generator and a 5 kW Phillips tube source. We have also developed a novel ultra-low q SALS instrument which is capable of measurements up to several millimeters in size [paper in preparation]. This instrument has been useful in investigating mixing in polymer/solvent systems, inhomogeneties in elastomers, large scale agglomeration in powders, and in a project with P&G looking at a scaling description of fiber morphology in non-woven fabrics. The USALS instrument is based on critical reflection rather than the diffraction optics currently used in x-ray cameras. We plan to extent this approach to x-rays and should theoretically be able to enhance the resolution of current Bonse-Hart cameras using this approach. The State of Ohio has funded the development of a pinhole SAXS camera under an instrumentation grant aimed at the study of silica and titania powders which is in collaboration with S. Pratsinis of the Chemical Engineering Department at UC with whom we have worked closely on inorganic powders. We are frequent users of the NIST Bonse-Hart Camera at BNL, as well as SANS and SAXS facilities at NIST, ORNL, Argonne, Sandia/UNM and Los Alamos.
Scattering Theory: Unfunded efforts in support of other projects.
Students Involved: Sathish Sukumaran, PhD Candidate.
SukumaSH@email.uc.edu
Shrish Rane, PhD Candidate
ranesy@email.uc.edu
ST1: Small-Angle Scattering from Polymeric Mass Fractals of Arbitrary Mass-Fractal Dimension, Beaucage, G. , J. Appl. Crystallogr. (1996), 29, 134-146.
ST2: Approximations leading to a unified exponential/power-law approach to small-angle scattering, Beaucage, G., J. Appl. Crystallogr. (1995), 28(6), 717-28.
ST3: Structural studies of complex systems using small-angle scattering: a unified Guinier/power-law approach, Beaucage, G; Schaefer, D. W, J. Non-Cryst. Solids (1994), 172-174(Pt. 2), 797-805.
A series of three papers were published concerning a new approach to the analysis small-angle scattering. The so called unified approach [ST1-3] provides a framework for dealing with scattering data that display multiple power-law and Guinier regimes. Generally, scattering laws are defined for small ranges of scattering vector, q. Examples of these are Porod's law, surface fractal power-laws, Guinier's law, and mass fractal power-laws. For some select cases scattering laws which deal with two regimes have been developed. Examples of these are the Debye Law for Polymer coils, the Debye-Bueche equation, special functions for spheres and rods and the Fischer-Burford equation for mass-fractals. In the unified approach a scattering pattern can be decomposed into one or more levels of structure each of which corresponds to a Guinier regime and a power-law regime. The unified approach describes both how a Guinier regime is related to a power-law regime within a level of structure, as well as how a series of related levels of structure can be joined to describe the compound scattering pattern from a complex material. It can be used, for example, to model polymer coils where the chain dimension deviates from a random walk [ST1]. It can also be used to describe the scaling transition from a Gaussian to a 1-d regime at the persistence length [PB1]. The unified approach is quite general. It has been applied to both surface and mass-fractals [F1-5, 10-15,17-18] as well as low-dimensional structures [C1].
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