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Small-angle and surface scattering from porous and fractal materials.

Description: We review the basic theoretical methods used to treat small-angle scattering from porous materials, treated as general two-phase systems, and also the basic experimental techniques for carrying out such experiments. We discuss the special forms of the scattering when the materials exhibit mass or surface fractal behavior, and review the results of recent experiments on several types of porous media and also SANS experiments probing the phase behavior of binary fluid mixtures or polymer solutions confined in porous materials. Finally, we discuss the analogous technique of off-specular scattering from surfaces and interfaces which is used to study surface roughness of various kinds.
Date: September 18, 1998
Creator: Sinha, S. K.
Partner: UNT Libraries Government Documents Department

The structure of carbon black-elastomer composites by small-angle neutron scattering and the method of contrast variation

Description: We have been exploring the use of small-angle neutron scattering and the method of contrast variation to give a new look at a very old problem: reinforcement of elastomers by carbon black in durable rubber products. Carbon black has a hierarchy of structures consisting of particles covalently bound into aggregates, which in turn associate by weak interactions into agglomerates. We found that in one carbon black, HSA, the aggregates are rodlike, containing an average of 4-6 particles. The aggregates have an outer graphitic shell and an inner core of lower density carbon. The core is continuous throughout the carbon black aggregate. Contrast variation of swollen HSA-polyisoprene gels shows that the HSA is completely embedded in polyisoprene and that the agglomerates are formed predominantly by end on associations of the rodlike aggregates. The surface structure of the carbon black appears smooth over length scales above about 10 {angstrom}. Further studies using production carbon blacks suggest that these structural characteristics are generally present in commercial rubber composites.
Date: July 1, 1996
Creator: Hjelm, R.P.; Wampler, W. & Gerspacher, M.
Partner: UNT Libraries Government Documents Department

Microphase separation in a model graft copolymer

Description: We present a preliminary overview of our work on a series of graft copolymers having poly(ethyl acrylate) backbones with pendant chains of polystyrene (PS). The copolymer system appeared to be in the strong segregation limit and exhibited evidence of ordered structures. The morphology of these structures can apparently be very different from what would be expected. For instance, we observed a lamellar structure in a material containing 28 wt.% PS grafts. Samples under uniaxial strain showed either conventional (i.e., affine deformation) and anomalous ({open_quotes}butterfly{close_quotes} isointensity patterns) behavior in small-angle neutron scattering.
Date: October 1, 1993
Creator: Dozier, W.D.; Thiyagarajan, P. & Peiffer, D.G.
Partner: UNT Libraries Government Documents Department

Void morphology in polyethylene/carbon black composites

Description: A combination of small angle neutron scattering (SANS) and contrast matching techniques is used to determine the size and quantity of voids incorporated during fabrication of polyethylene/carbon black composites. The analysis used to extract void morphology from SANS data is based on the three-phase model of microcrack determination via small angle x-rayscattering (SAXS) developed by W.Wu{sup 12} and applied to particulate reinforced composites.
Date: December 31, 1996
Creator: Marr, D.W.M.; Wartenberg, M. & Schwartz, K.B.
Partner: UNT Libraries Government Documents Department

Measurements of near forward scattered laser light in a large ICF plasma

Description: We describe an instrument which measures the angular spread and spectrum of near forward scattered laser light from a probe beam in a long scalelength laser-plasma. The instrument consists of a combination of time integrating and time resolving detectors which measure the scattered light amplitude over four orders of magnitude for a range of angles. These measurements allow us to study the beam spray resulting from various laser and plasma conditions and determine the density fluctuations associated with this beam spray.
Date: June 2, 1998
Creator: Moody, J. D.
Partner: UNT Libraries Government Documents Department

Small angle neutron and X-ray scattering studies of carbons prepared using inorganic templates

Description: Small angle neutron (SANS) and X-ray (SAXS) scattering analyses of carbons derived from organic-loaded inorganic template materials, used as anodes in lithium ion cells, have been performed. Two clays were used as templates to load the organic precursors, pillared montmorrillonite (PILC), a layered silicate clay whose sheets have been permanently propped open by sets of thermally stable molecular props, and sepiolite, a natural channeled clay. Five different organic precursors were used to load the PILC: pyrene, styrene, pyrene/trioxane copolymer, ethylene and propylene, whereas only propylene and ethylene were used to load sepiolite. Pyrolysis took place at 700{degrees}C under nitrogen. Values such as hole radius, fractal dimension, cutoff length and density of the final carbons will be compared as a function of the clay and carbon precursors.
Date: September 1, 1997
Creator: Sandi, G.; Thiyagarajan, P.; Winans, R.E. & Carrado, K.A.
Partner: UNT Libraries Government Documents Department

Characterization of fullerenes and fullerene derivatives by small-angle neutron scattering and transmission measurements

Description: Small-angle neutron scattering (SANS) has been shown to be an appropriate technique for the structural characterization of fullerenes (1) in solvents with strong SANS contrast (e.g. CS{sub 2}) and we have extended initial studies of C{sub 60} (1) to include C{sub 70} and C{sub 84} moieties. Deuterated solvents (e.g. toluene-d{sub 8}) have a high scattering length density (SLD), which is close to that of C{sub 60}, so there is virtually no SANS contrast with the solvent. Hence, these particles are practically {open_quotes}invisible{close_quotes} in such media, though the negative scattering length of hydrogen means that SLD of H{sup 1}-containing materials is much lower, so they have strong contrast with toluene-d{sub 8}. Thus, SANS makes it possible to study the size and shapes of modified buckyballs and this paper describes the first results on cyclohexane-substituted fullerenes.
Date: January 1, 1997
Creator: Melnichenko, Y.B.; Wignall, G.D. & Affholter, K.A.
Partner: UNT Libraries Government Documents Department

Small angle neutron scattering studies of vesicle stability

Description: Small angle neutron scattering (SANS) was used to investigate the structure of mixed colloids of egg yolk phosphatidylcholine (EYPC) with the bile salt, cholylglycine (CG), in D{sub 2}O as a function of pressure (P) and temperature (T). At atmospheric pressure, the system forms an isotropic phase of mixed, single bilayer vesicles (SLV`s). Increasing the external hydrostatic pressure brought about significant changes in particle morphology. At T = 25 C, application of a pressure of 3.5 MPa resulted in the collapse of the SLV`s. Further increase of P, up to 51.8 MPa, resulted in a transition from a phase of ordered (stacked), collapsed vesicles to one of stacked, ribbon-like particles. A similar collapse of the vesicles was observed at higher temperature (T = 37 C) with increasing P, but at this temperature, no ribbon phase was found at the highest pressure explored.
Date: October 1, 1997
Creator: Mang, J.T. & Hjelm, R.P.
Partner: UNT Libraries Government Documents Department

Effect of a solid/liquid interface on bulk solution structures under flow

Description: It has been known for some time that a shear field can impart enough energy to a liquid system for it to exhibit a phase change. Not as well appreciated is the fact that non Newtonian solutions can be driven into a quasi phase separation due to the vastly different shear rates between the bulk and near surface regions. Using a variety of scattering techniques the authors have probed the interfacial and near surface region of a system of wormlike colloidal particles under flow separately from the bulk. They find that the hexagonal phase which forms under flow near the surface, does not persist into the bulk. They also present data showing substantial differences in the kinetics of alignment and relaxation of the two phases.
Date: July 15, 1997
Creator: Butler, P. D.; Hamilton, W. A.; Hayter, J. B.; Magid, L. J. & Slawecki, T. M.
Partner: UNT Libraries Government Documents Department

An overview of resid characterization by mass spectrometry and small angle scattering techniques.

Description: The purpose of this presentation is to discuss what is known about the molecular structures found in petroleum resid from mass spectrometry and small angle neutron and X-ray scattering methods. The question about molecular size distributions and the occurrence of aggregation in the asphaltene fraction will be examined. Our understanding of this problem has evolved with the application of new analytical methods. Also, correlations with results from other approaches will be discussed. In addition, the issue of the nature of the heteroatom-containing molecules will be examined and the challenges that remain in this area.
Date: July 14, 1999
Creator: Hunt, J. E. & Winans, R. E.
Partner: UNT Libraries Government Documents Department

Interaction of polymer with clays.

Description: Normally synthetic well defined monodisperse discotic laponite clays are known to form a gel phase at mass concentrations as low as a few percent in distilled water. Hydrosoluble polymer polyethylene oxide was added to this intriguing clay system, it was observed that it either prevents gelation or slows it down extremely depending on the polymer weight, concentration or the laponite concentration. Small Angle Neutron scattering (SANS) was used to study these systems because only by isotopic labelling can the structure of the adsorbed polymer layers be determined. The contrast variation technique is specifically used to determine separately the different partial structure factors of the clay and polymer. In this way the signal of the adsorbed chains is separated from the signal of the free chains.
Date: July 2, 1999
Creator: Auvray, L. & Lal, J.
Partner: UNT Libraries Government Documents Department

Small-angle neutron-scattering study of nanophase zirconia in a reverse micelle synthesis.

Description: Nanophase zirconia particles are synthesized by mixing two reverse micelle solutions containing the precursor salt ZrOCl{sub 2} and the base NH{sub 4}OH. The primary reverse micelle solution consists of AOT, toluene and water. The reverse micelle structure of four solutions as a function of w (the molar ratio of [water]/[AOT]) is characterized by small-angle neutron scattering at room temperature. With the addition of ZrOCl{sub 2} and NH{sub 4}OH into the water pools, the reverse micelle sizes decrease as compared to those in the D{sub 2}O/AOT/C{sub 6}D{sub 5}CD{sub 3} primary system. The mixed microemulsions contain reverse micelle sizes that fail between the values of the pre-mixed solutions. All the reverse micelles exhibit uniform size and spherical shape. The effect of concentration of inorganic salt precursor in the water pools on the reverse micelle structure is also studied.
Date: July 2, 1999
Creator: Lager, G. A.; Li, X.; Loong, C.-K.; Miranda, R. & Thiyagarajan, P.
Partner: UNT Libraries Government Documents Department

SANS study of phase separation in solid {sup 3}He-{sup 4}He

Description: Small angle neutron scattering has been used to study phase separation in a quantum alloy, solid {sup 3}He{sub x}-{sup 4}He{sub 1{minus}x}. The onset of phase separation is marked by a dramatic increase in the measured scattering. A simple interpretation of the results suggests that the late-stage phase separation kinetics are dominated by an increase in the concentration of {sup 3}He atoms in preexisting precipitate regions.
Date: December 31, 1994
Creator: Koster, J.P.; Nagler, S.E.; Adams, E.D. & Wignall, G.D.
Partner: UNT Libraries Government Documents Department

Small angle neutron scattering (SANS) and small angle x-ray scattering (SAXS) analysis of polyaniline salts and blends

Description: Doped polyaniline emeraldine salts (PANI-ES) exhibit good environmental stability with a high level of conductivity (1 to 300 S/cm). However, they suffer from the fact that they have poor mechanical properties and must be blended with an insulating host polymer to be useful in industrial applications. Polyaniline blends are a new type of conducting material that typically show very low onsets of conductivity unlike that of metal filled blends. This is primarily due to the unique cellular geometry of the PANI-ES that is formed within the insulating host polymer. The formation of this immiscible polymer network may be due in part to structural and conformational differences in the blend components.
Date: June 1, 1996
Creator: Hopkins, A.R.; Rasmussen, P.G.; Basheer, R.A.; Annis, B.K. & Wignall, G.D.
Partner: UNT Libraries Government Documents Department

The new small-angle diffractometer SAND at IPNS

Description: A new small-angle neutron diffractometer SAND is undergoing commissioning at IPNS pulsed source. This paper provides details of the design and expected performance of this instrument.
Date: December 31, 1995
Creator: Crawford, R.K.; Thiyagarajan, P.; Epperson, J.E.; Trouw, F.; Kleb, R.; Wozniak, D. et al.
Partner: UNT Libraries Government Documents Department

Structural characterization of a polymer substituted fullerene (flagellene) by small angle neutron scattering

Description: Small-angle neutron scattering (SANS) can structurally characterize fullerenes in solvents with strong SANS contrast (e.g. CS{sub 2}). Deuterated solvents (e.g. toluene-d{sub 8}) have a high scattering length density (SLD), which is close to that of C{sub 60} and C{sub 70} moieties. Hence, there is virtually no SANS contrast with the solvent and these particles are practically ``invisible`` in such media. On the other hand, the negative scattering length of hydrogen means that the SLD of H{sup 1}-containing materials is much lower, so they have strong contrast with toluene-d{sub 8}. Thus, SANS makes it possible to study the size and shapes of modified buckyballs such as the polymer-substituted fullerenes, or flagellenes. These consist of C{sub 60} cores to which 1-4 polystryene chains (with a molecular weight, MW {approx_equal} 2000) are attached. The extrapolated cross section at zero angle of scatter [d{Sigma}/d{Omega}(0)] is a function of the number of pendant chains, so SANS can be used to assess the number of ``arms`` which are covalently attached to the fullerene ``sphere.`` Close agreement ({plus_minus}4%) between measured and calculated values of d{Sigma}/d{Omega}(0) along with independent estimates of the radius of gyration (R{sub g}) and second virial coefficient (A{sub 2}) for a calibration linear polystyrene sample serves as a cross check on the validity of this methodology.
Date: December 31, 1994
Creator: Affholter, K.A.; Bunick, G.J.; Wignall, G.D.; Desimone, J.M.; Hunt, M.O. Jr.; Menceloglu, Y.Z. et al.
Partner: UNT Libraries Government Documents Department

Electrochemical in-situ reaction cell for X-ray scattering, diffraction and spectroscopy

Description: An electrochemical in-situ reaction cell for hard X-ray experiments with battery electrodes is described. Applications include the small angle scattering, diffraction, and near-edge spectroscopy of lithium manganese oxide electrodes.
Date: January 27, 2003
Creator: Braun, Artur; Granlund, Eric & Cairns, Elton J.
Partner: UNT Libraries Government Documents Department

Phase Behavior of Blends of Linear and Branched Polyethylenes on Micron-Length Scales via Ultra-Small-Angle Neutron Scattering (USANS)

Description: SANS experiments on blends of linear, high density (HD) and long chain branched, low density (LD) polyethylenes indicate that these systems form a one-phase mixture in the melt. However, the maximum spatial resolution of pinhole cameras is approximately equal to 10<sup>3</sup>Å and it has therefore been suggested that data might also be interpreted as arising from a bi-phasic melt with large a particle size (~ 1 µm), because most of the scattering from the different phases would not be resolved. We have addressed this hypothesis by means of USANS experiments, which confirm that HDPEILDPE blends are homogenous in the melt on length scales up to 20 µm. We have also studied blends of HDPE and short-chain branched linear low density polyethylenes (LLDPEs), which phase separate when the branch content is sufficiently high. LLDPEs prepared with Ziegler-Natta catalysts exhibit a wide distribution of compositions, and may therefore be thought of as a �blend� of different species. When the composition distribution is broad enough, a fraction of highly branched chains may phase separate on µm-length scales, and USANS has also been used to quantify this phenomenon.
Date: May 17, 1999
Creator: Agamalian, M.M.; Alamo, R.G.; Londono, J.D.; Mandelkern, L. & Wignall, G.D.
Partner: UNT Libraries Government Documents Department

Small angle neutron scattering from nanocrystalline Pd and Co compacted at elevated temperatures

Description: Nanocrystalline (n-) Cu and Pd, prepared by inert gas condensation and in situ room temperature (RT) and elevated temperature (warm) compactions, have been studied by small angle neutron scattering (SANS). Previous work on RT compacted and subsequently annealed n-Pd seemed to show that all the scattering could be accounted for by a distribution of pores. Analysis of more extensive SANS measurements, together with results of prompt gamma activation analysis, indicates that the SANS can be explained by the presence of pores and hydrogen. Warm compaction reduces the hydrogen impurity level, while increasing the bulk density and decreasing the pore size. This can lead to a dramatic hardness increase in these materials.
Date: May 1, 1994
Creator: Sanders, P. G.; Weertman, J. R.; Barker, J. G. & Siegel, R. W.
Partner: UNT Libraries Government Documents Department

Nanostructure of a-Si:H and related alloys by small-angle scattering of neutrons and X-rays: Annual technical progress report: May 22, 1998 -- May 21, 1999

Description: This report describes work being performed to provide details of the microstructure in high-quality hydrogenated amorphous silicon and related alloys on the nanometer scale. The materials under study are being prepared by state-of-the-art deposition methods, as well as by new and emerging deposition techniques. The purpose is to establish the role of nanostructural features in controlling opto-electronic and photovoltaic properties. The approach centers around the use of the uncommon technique of small-angle scattering of both X-rays (SAXS) and neutrons (SANS). SAXS has already been established as highly sensitive to microvoids and columnar-like microstructure. A major goal of this research is to establish the sensitivity of SANS to the hydrogen nanostructure. Conventional X-ray diffraction techniques are being used to examine medium-range order and microcrystallinity, particularly near the boundary between amorphous and microcrystalline material.
Date: December 21, 1999
Creator: Williamson, D. L.
Partner: UNT Libraries Government Documents Department

SIBYLS - A SAXS and protein crystallography beamline at the ALS

Description: The new Structurally Integrated BiologY for Life Sciences (SIBYLS) beamline at the Advanced Light Source will be dedicated to Macromolecular Crystallography (PX) and Small Angle X-ray Scattering (SAXS). SAXS will provide structural information of macromolecules in solutions and will complement high resolution PX studies on the same systems but in a crystalline state. The x-ray source is one of the 5 Tesla superbend dipoles recently installed at the ALS that allows for a hard x-ray program to be developed on the relatively low energy Advanced Light Source (ALS) ring (1.9 GeV). The beamline is equipped with fast interchangeable monochromator elements, consisting of either a pair of single Si(111) crystals for crystallography, or a pair of multilayers for the SAXS mode data collection (E/{Delta}E {approx} 1/110). Flux rates with Si(111) crystals for PX are measured as 2 x 10{sup 11} hv/sec/400 mA through a 100 {micro}m pinhole at 12.4 KeV. For SAXS the flux is up to 3 x 10{sup 13} photons/sec at 10 KeV with all apertures open when using the multilayer monochromator elements. The performance characteristics of this unique beamline will be described.
Date: August 22, 2003
Creator: Trame, Christine; MacDowell, Alastair A.; Celestre, Richard S.; Padmore, Howard A.; Cambie, Daniella; Domning, Edward E. et al.
Partner: UNT Libraries Government Documents Department

SUNY beamline facilities at the National Synchrotron Light Source (Final Report)

Description: The DOE sponsored SUNY synchrotron project has involved close cooperation among faculty at several SUNY campuses. A large number of students and postdoctoral associates have participated in its operation which was centered at the X3 beamline of the National Synchrotron Light Source at Brookhaven National Laboratory. Four stations with capabilities for Small Angle Scattering, Single Crystal and Powder and Surface diffraction and EXAFS were designed and operated with capability to perform experiments at very low as well as elevated temperatures and under high vacuum. A large amount of cutting-edge science was performed at the facility, which in addition provided excellent training for students and postdoctoral scientists in the field.
Date: June 22, 2003
Creator: Coppens, Philip
Partner: UNT Libraries Government Documents Department

A Proposal to Study Small Angle Proton-Deuteron Scattering

Description: We propose an extension of the present p-p small angle scattering experiment to a measurement of p-d scattering using a deuterium gas jet. In 400 hours of beam time we will measure as a function of energy; (a) the slope of the small angle p-d scattering; (b) the real part of the forward p-d scattering; (c) the total p-d cross section; and (d) the coherent diffraction dissociation of protons on deuterons. No new apparatus is required or need be installed for the performance of this experiment.
Date: September 22, 1972
Creator: Bartenev, V.; Kuznetsov, A.; Morozov, B.; Nikitin, N.; Pilipenko, Y.; Popov, V. et al.
Partner: UNT Libraries Government Documents Department