Using Ultra Small Angle X-ray Scattering Research Articles

Insights into the Biomimetic Synthesis of 2D ZnO Nanomaterials through Peptoid Engineering.

Achieving predictable biomimetic crystallization using sequence-defined synthetic molecules in mild conditions represents a long-standing challenge in materials synthesis. Herein we report a peptoid-based approach for biomimetic control over the formation of nanostructured ZnO materials in ambient aqueous conditions. A series of two-dimensional (2D) ZnO nanomaterials have been successfully obtained using amphiphilic peptoids with different numbers, ratios, and patterns of various hydrophilic and hydrophobic side chains. By investigating the relationship between peptoid hydrophobicity and the thickness of the resultant ZnO nanomaterials, we found the critical role of peptoid hydrophobicity in the peptoid-controlled ZnO formation. Our results suggest that tuning the hydrophobicity of peptoids can be used to moderate peptoid-ZnO surface interactions, thus controlling the formation of ultrathin (<2.5 nm) 2D ZnO nanomaterials. The peptoid-controlled formation of ZnO nanomaterials was further investigated using ultrasmall-angle X-ray scattering (USAXS). Our work suggests a new approach to synthesizing 2D metal oxide nanomaterials using sequence-defined synthetic molecules.

Multiscale Relaxation Behavior of Amorphous Plasticized Poly(vinyl butyral).

As a key component in laminated glass, plasticized polyvinyl butyral (PVB) interlayer is a kind of impact resistant polymer material with high toughness. Recently, by using ultra-small angle X-ray scattering (USAXS) technique, we have reported that stretch-induced phase separated structure on the scale of hundreds of nanometers formed in plasticized PVB for the first time. In this work, the multiscale relaxation behavior of plasticized PVB was further investigated. The relaxation behavior of deformed plasticized PVB was studied from macroscopic stress, mesoscopic phase separated structure and microscopic chain segment by combining USAXS, birefringence with in-situ stretching device. The contributions of chain segments and hydrogen bonding clusters for the multiscale relaxation behavior are discussed. This article is protected by copyright. All rights reserved.

Effects of Ink Formulation on the Structure and Performance of PGM-Free Catalyst Layer in PEMFCs

Platinum group metal (PGM) catalysts are the major electrocatalysts for oxygen reduction reaction (ORR) in the polymer electrolyte membrane fuel cells (PEMFCs). However, the cost of PGM catalysts is very high. Particular, the cost becomes unaffordable if the PEMFC is in massive application. In order to remove this cost obstacle of fuel cell commercialization, PGM-free catalysts have been considered as the replacement of PGM catalysts for ORR because of the low cost and the reasonable performance. Fe-C-N complex is the one of the most active centers in PGM-Free catalyst groups. This type of catalyst shows very promising activity in rotation disk electrode (RDE) testing. The half wave potential could reach 0.91 V versus standard hydrogen electrode (SHE). However, in a membrane electrode assembly (MEA), the performance of PGM-Free catalysts is not good enough to replace the PGM catalysts. Since the PGM-free catalysts are so different from the PGM catalysts in terms of catalytic activity, stability, surface conditions, particle size etc, the fabrication of PGM-Free catalyst MEA cannot simply copy the method of making PGM MEA. In addition, the thicknesses of catalyst layers of PFM-free are significantly thicker than that of PGM, for example, 10 times. We proposed a novel method of fabricating PGM-Free catalyst MEA, so that the intrinsic catalyst activity from RDE can be translated into MEA performance. The method is based on the catalyst coated membrane (CCM) method using optimized ionomer to carbon (I/C) ratio and solvent mixture of catalyst ink. Using this method, the PGM-free catalyst MEA achieved the current density 44.9 mA cm-2 at 0.9 ViR-free in H2/O2 and 150 mA cm-2 at 0.8 V in H2/air, which surpassed the performance targets of US Department of Energy (DOE) for PGM-Free catalyst MEA. The property (solvent composition, dispersion of catalyst and ionomer in an ink), structure (pore structure) and the MEA performance have been characterized using ultra-small angle x-ray scattering (USAXS), cyro-TEM, mercury intrusion porosimetry (MIP), SEM/EDAX, RDE and MEA testing. A property-structure-performance relationship has been established.

The relationship between ultra-small-angle X-ray scattering and viscosity measurements of casein micelles in skim milk concentrates

Skim milk concentrates have important applications in the dairy industry, often as intermediate ingredients. Concentration of skim milk by reverse osmosis membrane filtration induces water removal, which reduces the free volume between the colloidal components, in particular the casein micelles. Thermal treatment before or after concentration impacts the morphology of casein micelles. These changes affect the flow behavior and viscosity, but the consequences for supermicellar structure have not been elucidated. In the present study, skim milk concentrates with different total solid contents from 8.7% (control) up to 22.8% (w/w), prepared by reverse osmosis membrane filtration of non-heated and pasteurized skim milk, were heat treated at 75 °C for 18 s, and compared with non-heated concentrates. The structure of the concentrates was studied using Ultra Small Angle X-ray Scattering (USAXS), and the viscosity of concentrates was measured. The USAXS intensity I(q) was fitted at small and intermediate q-regions (0.0005 < q < 0.003 Å−1 and 0.0035 < q < 0.03 Å−1, respectively) with a power law. The value of the power law exponent was used to assess the heat- and concentration-induced aggregation of the milk solids and correlate it with the apparent viscosity. The results showed that increased viscosity of skim milk concentrates, due to water removal and heat-load, can be explained by increased aggregation of the casein micelles into elongated aggregates and increased smoothening of the casein micelle surface.

Influence of Silane Coupling Agents on Filler Network Structure and Stress-Induced Particle Rearrangement in Elastomer Nanocomposites.

Filled rubber materials are key in many technologies having a broad impact on the economy and sustainability, the most obvious being tire technology. Adding filler dramatically improves the strength of rubber by reinforcement and tailoring the type of filler, and the chemistry of the interface between the filler and rubber matrix is important for optimizing performance metrics such as fuel efficiency. In a highly loaded, silica-filled, cross-linked model rubber closely mimicking commercial materials, both the filler network structure and the dynamics of the silica filler particles change when the silica surface is modified with silane coupling agents. Reduction in size scales characteristic of the structure is quantified using ultra-small-angle X-ray scattering (USAXS) measurements and the particle dynamics probed with X-ray photon correlation spectroscopy (XPCS). While the structure averaged over the scattering volume changes little with aging after step strain, the dynamics slow appreciably in a manner that varies with the treatment of the silica filler. The evolution of filler particle dynamics depends on the chemical functionality at the silica surface, and observing these differences suggests a way of thinking about the origins of hysteresis in nanoparticle-reinforced rubbers. These microscopic filler dynamics are correlated with the macroscopic stress relaxation of the filled materials. The combination of static and dynamic X-ray scattering techniques with rheological measurements is a powerful approach for elucidating the microscopic mechanisms of rubber reinforcement.

Evaluation of nano/submicro pores in suspension plasma sprayed YSZ coatings

Nano-submicro pores could considerably influence the coating performances and thus should be properly designed for the intended applications. However, it is challenging to characterize accurately such small pores in coatings. In this study, YSZ coatings were firstly manufactured by suspension plasma spray (SPS) and the nano-submicro pores in as-prepared coatings were investigated using Ultra-small-angle X-ray scattering (USAXS). Afterwards, a multivariate analysis on the effect of five different process parameters was carried out. The two main results showed that: 1) the nano-submicro pores content in coatings has a negative correlation with suspension mass load and powder size, and a positive correlation with spray distance, spray step, and substrate surface roughness; 2) suspension mass load is the main factor affecting the content of nano-submicro pores. Then, a mathematical model for the prediction of nano-submicro pores was developed, and the control of nano-submicro pores content by using the predictive model was presented. Finally, the sintering effect on the evolution of nano-submicro pores was studied in-situ using USAXS as well.

Investigation of Voids in Polyacrylonitrile Fibers by USAXS and SAXS

The void structure of polyacrylonitrile(PAN) fibers was investigated using ultra-small angle X-ray scat-tering(USAXS) and small angle X-ray scattering(SAXS). A quantitative method was developed to analyze connected USAXS/SAXS data and thus determine the void parameters of PAN fibers. The results showed that voids affected the mechanical performance of PAN fibers and were present throughout the entire wet-spinning process. When the abso-lute quantity and size of voids decreased, the tensile strength and modulus of PAN fibers increased. The void para-meters were optimized by controlling the production process, and thus the tensile strength and modulus of PAN fibers were increased. The method for analyzing the void structure developed in this study is useful for analyzing voids over with larger size range, as well as the effect of the void structure on the mechanical performance of fibers.

Ultra-SAXS observation of fibril-sized structure formation after the necking of poly(ethylene terephthalate) and poly(phenylene sulfide) fibers

Fibril-sized structures, which exhibit a density fluctuation of several tens to hundreds of nanometers, are important because they influence many properties of fibers and films, particularly the strength and thermal shrinkage of synthetic fibers. We analyzed the formation of fibril-sized structures after necking using ultra-small-angle X-ray scattering (USAXS), which enables observation of the void and craze formations. Continuous laser-heated drawing and undulator synchrotron radiation were adopted to measure the structural development of poly(ethylene terephthalate) (PET) and poly(phenylene sulfide) (PPS) fibers. Both fibers showed a clear increase in the meridional streak intensity just after necking and an increase in the equatorial streak after necking. These increases were distinctive for PPS. Moreover, a layer-lined streak appeared after necking only for PET. The intensity of the meridional streak increased with an increase in the draw ratio, whereas the intensity of the layer-lined scattering decreased with an increase in the draw ratio. The change of ultra-small-angle X-ray scattering (USAXS) image after necking was taken for poly(ethylene terephthalate) (PET) and poly(phenylene sulfide) (PPS) fibers. USAXS pattern of PPS shows three streaks, which were meridional and equatorial streaks and total reflection. In addition to the three streaks observed for PPS, USAXS pattern of PET shows a layer-lined streak. Far stronger meridional streak of PPS means the periodic density deviation preliminary formed in the as-spun fiber, and the layer-lined USAXS streak of PET could be explained by the periodic bundle of a fibrillar-shaped smectic phase.

USAXS analysis of concentration-dependent self-assembling of polymer-brush-modified nanoparticles in ionic liquid: [I] concentrated-brush regime.

Using ultra-small angle X-ray scattering (USAXS), we analyzed the higher-order structures of nanoparticles with a concentrated brush of an ionic liquid (IL)-type polymer (concentrated-polymer-brush-modified silica particle; PSiP) in an IL and the structure of the swollen shell layer of PSiP. Homogeneous mixtures of PSiP and IL were successfully prepared by the solvent-casting method involving the slow evaporation of a volatile solvent, which enabled a systematic study over an exceptionally wide range of compositions. Different diffraction patterns as a function of PSiP concentration were observed in the USAXS images of the mixtures. At suitably low PSiP concentrations, the USAXS intensity profile was analyzed using the Percus-Yevick model by matching the contrast between the shell layer and IL, and the swollen structure of the shell and "effective diameter" of the PSiP were evaluated. This result confirms that under sufficiently low pressures below and near the liquid/crystal-threshold concentration, the studied PSiP can be well described using the "hard sphere" model in colloidal science. Above the threshold concentration, the PSiP forms higher-order structures. The analysis of diffraction patterns revealed structural changes from disorder to random hexagonal-closed-packing and then face-centered-cubic as the PSiP concentration increased. These results are discussed in terms of thermodynamically stable "hard" and/or "semi-soft" colloidal crystals, wherein the swollen layer of the concentrated polymer brush and its structure play an important role.

Shear-induced aggregation or disaggregation in edible oils: Models, computer simulation, and USAXS measurements

The effects of shear upon the aggregation of solid objects formed from solid triacylglycerols (TAGs) immersed in liquid TAG oils were modeled using Dissipative Particle Dynamics (DPD) and the predictions compared to experimental data using Ultra-Small Angle X-ray Scattering (USAXS). The solid components were represented by spheres interacting via attractive van der Waals forces and short range repulsive forces. A velocity was applied to the liquid particles nearest to the boundary, and Lees-Edwards boundary conditions were used to transmit this motion to non-boundary layers via dissipative interactions. The shear was created through the dissipative forces acting between liquid particles. Translational diffusion was simulated, and the Stokes-Einstein equation was used to relate DPD length and time scales to SI units for comparison with USAXS results. The SI values depended on how large the spherical particles were (250 nm vs. 25 nm). Aggregation was studied by (a) computing the Structure Function and (b) quantifying the number of pairs of solid spheres formed. Solid aggregation was found to be enhanced by low shear rates. As the shear rate was increased, a transition shear region was manifested in which aggregation was inhibited and shear banding was observed. Aggregation was inhibited, and eventually eliminated, by further increases in the shear rate. The magnitude of the transition region shear, γ̇t, depended on the size of the solid particles, which was confirmed experimentally.

Measurements of droplet size in shear-driven atomization using ultra-small angle x-ray scattering

Measurements of droplet size in optically-thick, non-evaporating, shear-driven sprays have been made using ultra-small angle x-ray scattering (USAXS). The sprays are produced by orifice-type nozzles coupled to diesel injectors, with measurements conducted from 1 – 24 mm from the orifice, spanning from the optically-dense near-nozzle region to more dilute regions where optical diagnostics are feasible. The influence of nozzle diameter, liquid injection pressure, and ambient density were examined. The USAXS measurements reveal few if any nanoscale droplets, in conflict with a popular computational model of diesel spray breakup. The average droplet diameter rapidly decreases with downstream distance from the nozzle until a plateau value is reached, after which only small changes are seen in droplet diameter. This plateau droplet size is consistent with the droplets being small enough to be stable with respect to further breakup. Liquid injection pressure and nozzle diameter have the biggest impact on droplet size, while ambient density has a smaller effect.

Microstructure Analysis of Polymer Electrolyte Membrane Fuel Cell Catalyst-Ionomer Inks and Cathode Catalyst Layers By Ultra Small Angle X-Ray Scattering

The successful development of novel materials for polymer electrolyte membrane fuel cell (PEMFC) electrodes is hindered by the lack of a fundamental understanding of the complex, multicomponent nature of the catalyst layer (CL), the interplay of its components, and their independent and cooperative effects on the effective properties. One of the most prevalent methods for preparing PEMFC membrane-electrode assemblies is the thin film decal transfer (DT) method, which involves dispersing the catalyst powder and perfluorosulfonic acid ionomer in a solvent media to form a catalyst ink, and then forming a porous thin film CL which is then transferred to the membrane via hot-pressing. To achieve maximum performance, the CL needs to have (i) the maximum interface of ionomer and catalyst for the anode and cathode reactions, (ii) the appropriate pore structure to allow gas and water diffusion, and (iii) ionomer networks that bind the carbon aggregates together, providing structural integrity for the catalyst layer and a proton conduction path. For optimization, the type of solvent, solvent-to-solids ratio, and ionomer-to-carbon ratio are variables which affect the resulting CL structure and performance. Characterization of both catalyst inks and catalyst layers is necessary to understand how processing, structure, properties, and performance are all related. In this study, a systematic approach was taken to study the microstructure of the catalyst ink formulations and the prepared CLs using ultra-small-angle X-ray scattering (USAXS). By combining USAXS with small angle X-ray scattering (USAXS-pinSAXS), it is possible to obtain scattered intensity spanning over several decades in scattering vector, q (q = 4πsinθ/l), which can provide size and structural information from 1 nm to 6 mm. USAXS-pinSAXS measurements were performed at the Advanced Photon Source (APS) at Argonne National Laboratory. Multiple-level curve fitting, using a suite of macros written for Igor Pro-based software, was used to extract from the scattering data the particle size, size distribution, and geometry of the carbon-supported Pt and Pt-alloy aggregates in catalyst-ionomer-solvent inks and catalyst layers. The USAXS-pinSAXS study showed formation of aggregated microstructures, which are different for the Pt and Pt-alloy catalyst inks and catalyst layers.

Condensation versus diffusion. A spatial-scale-independent theory of aggregate structures in edible oils: applications to model systems and commercial shortenings studied via rheology and USAXS

Understanding how solid fats structures come about in edible oils and quantifying their structures is of fundamental importance in developing edible oils with pre-selected characteristics. We considered the great range of fractal dimensions, from 1.91 to 2.90, reported from rheological measurements. We point out that, if the structures arise via DLA/RLA or DLCA/RLCA, as has been established using ultra small angle x-ray scattering (USAXS), we would expect fractal dimensions in the range ~1.7 to 2.1, and ~2.5 or ~3.0. We present new data for commercial fats and show that the fractal dimensions deduced lie outside these values. We have developed a model in which competition between two processes can lead to the range of fractal dimensions observed. The two processes are (i) the rate at which the solid fat particles are created as the temperature is decreased, and (ii) the rate at which these particles diffuse, thereby meeting and forming aggregates. We assumed that aggregation can take place essentially isotropically and we identified two characteristic times: a time characterizing the rate of creation of solid fats, , where is the rate of solid condensation (cm3 s−1), and the diffusion time of solid fats, , where is their diffusion coefficient and is the typical average distance that fats must move in order to aggregate. The intent of this model is to show that a simple process can lead to a wide range of fractal dimensions. We showed that in the limit of very fast solid creation, the fractal dimension is predicted to be that of DLCA, ~1.7, relaxing to that of RLCA, 2.0–2.1, and that in the limit of very slow solid creation, , the fractal dimension is predicted to be that obtained via DLA, ~2.5, relaxing to that of RLA, 3.0. We predict that, given a system which satisfies our model assumptions and which can either be cooled rapidly or cooled slowly to yield fractal dimensions and then . This is supported by both rheological [] and USAXS measurements [, ] even though the latter models do not conform to the assumptions of those presented here.

Ultra Small Angle X-Ray Scattering for Pure Tristearin and Tripalmitin: Model Predictions and Experimental Results

Computer simulations in a 3-dimensional cubic space were carried out to (a) model the formation of grains of the triacylglycerols (TAGs), pure tristearin (SSS) and tripalmitin (PPP), and (b) compute structure functions, S(q), of the resulting grain boundaries. It was found that the generally-accepted process of grain creation leading to the formation of grain boundaries yielded results in accord with experimental data while an alternative procedure which created grain boundaries in an ad hoc way, did not. For the models, it was found that S(q) exhibited a slope of approximately −2 for higher q-values and a slope of approximately −3 for lower values of q. Broad localized peaks were observed at q ≈ 0.32u − 1, where u indicates the units used to define the simulation space. The localized peaks, indicating the characteristic dimensions of the grain boundaries, predict that this size is d ≈ 11 u. Experimental studies were carried out on pure SSS and PPP, using Ultra Small Angle X-Ray Scattering (USAXS), in the region 1 × 10−4 A−1 < q < 6 10−2 A−1 A section of the scattering profiles observed were interpreted in terms of the surface fractal morphology of grain boundaries surrounding the nano-scale voids - nanovoids - in the material. It was observed that the average volume of the nanovoids were characterized by a radius of gyration R g1 of about 370 ± 20 nm for SSS and 437 ± 28 nm for PPP when the Unified Fit software was used. Not surprisingly, the surface fractal dimension, D s , associated with R g1 was similar for both SSS and PPP, giving D s(sss) ~ 2.1 and D s(ppp) ~ 2.2. This is in accord with an interpretation that the nanovoid boundaries are rough 2-dimensional surfaces. A slope of approximately −3.0 was observed for the region of 1 × 10−4 A−1 < q < 4 × 10−4 A−1 for both materials, indicating that the distribution of the grain boundary surfaces is random. These results are in complete accord with the predictions of the models. We found that 1 μ ≈ 500 A so that a model nanovoid size of ∼ 11u is in accord with the sizes deduced from radii of gyration.

Resolving Anisotropic Interfacial Phenomena Using, In Situ, Grazing Transmission Ultra-Small Angle X-Ray Scattering Together with Electrochemical Impedance Spectroscopy

Inherent to many electrochemical systems is phase formation at or near the electrode surface. Resolving these phases, in-situ, is challenging with the presence of the necessary electrolyte between the working and counter electrodes. The high X-ray flux available at the Advanced Photon Source (APS) allows these phases to be resolved, in-situ, using small angle X-ray scattering (SAXS) in a grazing transmission geometry shown below. Using this geometry, dimensions both parallel and perpendicular to the surface can be resolved, in-situ, concurrently with an electrochemical technique such as electrochemical impedance spectroscopy (EIS). In this work we show how combined SAXS and EIS is used to resolve unique nanoparticle-solvent interactions that occur in a deep eutectic solvent. Using Ultra-small angle X-ray scattering (USAXS), together with EIS, we were able to resolve ~ 100 nm sized layers that reside above Pd and Ag nanoparticle ensembles on a glassy carbon surface. This study was also performed on the high-energy pinhole SAXS setup, where the distance between the opposing layers was also resolved. While USAXS/SAXS provides information about the size, shape and structure of these phases, the EIS provides their electrochemical response for a comprehensive understanding of interfacial chemistry. These results show how combined USAXS/SAXS and EIS can be used as complementary techniques to resolve otherwise elusive electroactive phases at the interface of electrochemical systems. This technique is accessible through the general user program at the APS. Some general considerations of the experimental setup are presented, including: signal to noise, geometry and cell capabilities. An overview of beamline capabilities is also presented and consists of USAXS/pinSAXS, USAXS, wide angle X-ray scattering (WAXS), USAXS imaging and the high-energy pinhole SAXS setup. With these capabilities, the 15-ID-D beamline offers the potential for a wide variety of in-situ electrochemical experiments towards an understanding of elusive interfacial phenomena.

Ultra Small Angle X-Ray Scattering Characterization of Temperature-Sensitive Ferrogels Prepared Using Magnetic Nanoparticles

ABSTRACTTemperature-sensitive ferrogel prepared using Fe3O4 nanoparticles are characterized under varying temperature conditions. The nanoparticles were distributed in Nisopropylacrylamide (NIPAm) during their polymerization to form hydrogel. Particle distribution and agglomeration characteristics of the prepared ferrogels were investigated using ultra small angle x-ray scattering (USAXS) at various temperatures through the Lower Critical Solution Temperature (LCST). Transmission electron microscopy (TEM) was used to estimate the particle size distribution. The magnetic property was investigated using direct current superconducting quantum interference device (DC-SQUID) under hydrated conditions. The USAXS analysis showed an increase in the volume of particles without changing the agglomeration characteristics as the temperature is increased during the measurements. The ferrogel did not show any sedimentation or particle detachment from the gel under thermal cycling. Details of our results and analysis are presented.

Individual dispersion of carbon nanotubes in epoxy via a novel dispersion–curing approach using ionic liquids

The effective dispersion of carbon nanotubes (CNTs) in a thermoset was achieved using ionic liquid as the dispersion-curing agent. We preferentially dispersed multiwalled carbon nanotubes (MWCNTs) down to individual tube levels in epoxy resin. Here the dispersion is ruled by the depletion of physical bundles within the MWCNT networks, for which molecular ordering of ionic liquids is considered responsible. The quantitative analyses using ultra small angle X-ray scattering (USAXS) confirmed the dispersion of individual MWCNTs in the matrix. The distance between the dispersed nanotubes was calculated at different nanotube loadings using the power law fitting of the USAXS data. The fine dispersion and subsequent curing, both controlled by ionic liquid, lead to composites with substantially enhanced fracture mechanical and thermomechanical properties with no reduction in thermal properties. Merging processing techniques of nanocomposites with ionic liquid for efficient dispersion of nanotubes and preferential curing of thermosets facilitates the development of new, high performance materials.

Characterization of Fe3O4 and Fe2O3 ferrogels prepared under uniform magnetic field

ABSTRACTWe compare the characteristics of ferrogels prepared with and without the presence of a uniform magnetic field using Fe3O4 and Fe2O3 nanoparticles immobilized in hydrogels of N-isopropylacrylamide. The spatial distribution and agglomeration of the nanoparticles within the ferrogels were investigated using ultra small angle x-ray scattering (USAXS) and transmission electron microscopy (TEM). Hydrated ferrogels were also studied for magnetization using direct current superconducting quantum interference device (DC-SQUID). Volume size distribution resulting from USAXS data of the Fe3O4-ferrogel prepared under a uniform 225 G magnetic field showed a single broad peak appreciably different from that prepared without magnetic field with three distinct peaks. Volume size distributions resulting from USAXS data of the Fe2O3-ferrogel prepared with and without the presence of a uniform magnetic field both similarly show two peaks. Nanoparticle agglomeration was also determined by analyzing TEM images of ferrogel samples. DC-SQUID measurements of Fe3O4-ferrogel prepared in the presence of a uniform magnetic field showed 9% higher magnetization compared to the Fe3O4-ferrogel prepared without magnetic field. Similarly, DC-SQUID measurements of Fe2O3-ferrogel prepared in the presence of a uniform magnetic field showed 3% higher magnetization compared to the Fe2O3-ferrogel prepared without magnetic field. Thus, the presence of a uniform magnetic field during ferrogel polymerization can enabled the enhancement of the magnetoelastic property of the ferrogel.

Investigation of the Interaction of Nafion Ionomer and Carbon Black Using Small Angle X-ray and Small Angle Neutron Scattering

One of the major aims of this investigation is to fill the gap of the interaction of ionomer particles and Vulcan XC-72 (VXC-72) aggregates in a catalyst ink. The dispersion of catalyst ink not only depends on the solvent, but also depends on the interaction of Nafion and carbon particles in the ink. The interaction of Nafion® ionomer particles and Vulcan XC-72 catalyst aggregates in liquid media was studied using ultra small angle x-ray scattering (USAXS) and cryogenic TEM technologies. A Functionalized Vulcan XC-72 (FVXC-72) system was introduced to study the interaction behavior. A multiple curve fitting was used to extract the particle size, size distribution and geometry from scattering data. The results suggest that the particle size, size distribution and geometry of each system changed significantly from Nafion + Vulcan XC-72 system to Nafion + FVXC-72 system which indicated that interaction among components (i.e. ionomer particles and Vulcan XC-72 aggregates) exists. The cryogenic TEM, by which the size and geometry of particles in a liquid can be directly observed, was used to validate the scattering results, which shows the excellent agreement.

Investigation of Catalyst Ink Dispersion Using Small Angle X-ray and Small Angle Neutron Scattering

One of the major aims of this investigation is to fill the gap of the micro-structural organization of ionomer particles and Pt/C aggregates dispersed in a catalyst ink. The dispersion of Nafion® ionomer particles and Pt/C catalyst aggregates in liquid media was studied using ultra small angle x-ray scattering (USAXS) and cryogenic TEM technologies. A systematic approach was taken to study the dispersion of each component (i.e. ionomer particles and Pt/C aggregates) first, then the combination, last the catalyst ink. A multiple curve fitting was used to extract the particle size, size distribution and geometry from scattering data. The results suggest that the particle size, size distribution and geometry of each system are not uniform, rather, vary significantly. The results also indicate that interaction among components (i.e. ionomer particles and Pt/C aggregates) exists. The cryogenic TEM, by which the size and geometry of particles in a liquid can be directly observed, was used to validate the scattering results, which shows the excellent agreement. Based on this study, a methodology of analyzing dispersion of Pt/C particles, Nafion particles in a catalyst ink has been developed and it can serve as a powerful tool for making a desired catalyst ink which is the crtical step for making rational designed MEA.