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Instruments / Technical Area	Publication Details	Published
I22-Small angle scattering & Diffraction	In situ and ex situ X-ray diffraction and small-angle X-ray scattering investigations of the sol–gel synthesis of Fe3N and Fe3C Matthew S. Chambers , Robert D. Hunter , Martin J. Hollamby , Brian R. Pauw , Andrew J. Smith , Tim Snow , Ashleigh Danks , Zoe Schnepp Inorganic Chemistry DOI: 10.1021/acs.inorgchem.1c03442 Diamond Proposal Number(s): [11969] Open Access Show Abstract ▼ Abstract: Iron nitride (Fe3N) and iron carbide (Fe3C) nanoparticles can be prepared via sol–gel synthesis. While sol–gel methods are simple, it can be difficult to control the crystalline composition, i.e., to achieve a Rietveld-pure product. In a previous in situ synchrotron study of the sol–gel synthesis of Fe3N/Fe3C, we showed that the reaction proceeds as follows: Fe3O4 → FeOx → Fe3N → Fe3C. There was considerable overlap between the different phases, but we were unable to ascertain whether this was due to the experimental setup (side-on heating of a quartz capillary which could lead to thermal gradients) or whether individual particle reactions proceed at different rates. In this paper, we use in situ wide- and small-angle X-ray scattering (wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS)) to demonstrate that the overlapping phases are indeed due to variable reaction rates. While the initial oxide nanoparticles have a small range of diameters, the size range expands considerably and very rapidly during the oxide–nitride transition. This has implications for the isolation of Rietveld-pure Fe3N, and in an extensive laboratory study, we were indeed unable to isolate phase-pure Fe3N. However, we made the surprising discovery that Rietveld-pure Fe3C nanoparticles can be produced at 500 °C with a sufficient furnace dwell time. This is considerably lower than the previous reports of the sol–gel synthesis of Fe3C nanoparticles.	Apr 2022
I22-Small angle scattering & Diffraction	Extending synchrotron SAXS instrument ranges through addition of a portable, inexpensive USAXS module with vertical rotation axes Brian R. Pauw , Andrew Smith , Tim Snow , Olga Shebanova , John P. Sutter , Jan Ilavsky , Daniel Hermida-Merino , Glen J. Smales , Nicholas J. Terrill , Andreas F. Thünemann , Wim Bras Journal Of Synchrotron Radiation 28 DOI: 10.1107/S1600577521003313 Open Access Show Abstract ▼ Abstract: Ultra-SAXS can enhance the capabilities of existing synchrotron SAXS/WAXS beamlines. A compact ultra-SAXS module has been developed, which extends the measurable q-range with 0.0015 ≤ q (nm−1) ≤ 0.2, allowing structural dimensions in the range 30 ≤ D (nm) ≤ 4000 to be probed in addition to the range covered by a high-end SAXS/WAXS instrument. By shifting the module components in and out on their respective motor stages, SAXS/WAXS measurements can be easily and rapidly interleaved with USAXS measurements. The use of vertical crystal rotation axes (horizontal diffraction) greatly simplifies the construction, at minimal cost to efficiency. In this paper, the design considerations, realization and synchrotron findings are presented. Measurements of silica spheres, an alumina membrane, and a porous carbon catalyst are provided as application examples.	May 2021
I22-Small angle scattering & Diffraction	A template-free and low temperature method for the synthesis of mesoporous magnesium phosphate with uniform pore structure and high surface area Jorn Hovelmann , Tomasz M. Stawski , Rogier Besselink , Helen M. Freeman , Karen M. Dietmann , Sathish Mayanna , Brian R. Pauw , Liane G. Benning Nanoscale 11, 6939 - 6951 DOI: 10.1039/C8NR09205B Diamond Proposal Number(s): [16256] Open Access Show Abstract ▼ Abstract: Mesoporous phosphates are a group of nanostructured materials with promising applications, particularly in biomedicine and catalysis. However, their controlled synthesis via conventional template-based routes presents a number of challenges and limitations. Here, we show how to synthesize a mesoporous magnesium phosphate with a high surface area and a well-defined pore structure through thermal decomposition of a crystalline struvite (MgNH4PO4·6H2O) precursor. In a first step, struvite crystals with various morphologies and sizes, ranging from a few micrometers to several millimeters, had been synthesized from supersaturated aqueous solutions (saturation index (SI) between 0.5 and 4) at ambient pressure and temperature conditions. Afterwards, the crystals were thermally treated at 70–250 °C leading to the release of structurally bound water (H2O) and ammonia (NH3). By combining thermogravimetric analyses (TGA), scanning and transmission electron microscopy (SEM, TEM), N2 sorption analyses and small- and wide-angle X-ray scattering (SAXS/WAXS) we show that this decomposition process results in a pseudomorphic transformation of the original struvite into an amorphous Mg-phosphate. Of particular importance is the fact that the final material is characterized by a very uniform mesoporous structure with 2–5 nm wide pore channels, a large specific surface area of up to 300 m2 g−1 and a total pore volume of up to 0.28 cm3 g−1. Our struvite decomposition method is well controllable and reproducible and can be easily extended to the synthesis of other mesoporous phosphates. In addition, the so produced mesoporous material is a prime candidate for use in biomedical applications considering that magnesium phosphate is a widely used, non-toxic substance that has already shown excellent biocompatibility and biodegradability.	Apr 2019
	The modular small-angle X-ray scattering data correction sequence B. R. Pauw , A. J. Smith , T. Snow , N. J. Terrill , A. F. Thünemann Journal Of Applied Crystallography 50, 1800 - 1811 DOI: 10.1107/S1600576717015096 Open Access Show Abstract ▼ Abstract: Data correction is probably the least favourite activity amongst users experimenting with small-angle X-ray scattering: if it is not done sufficiently well, this may become evident only during the data analysis stage, necessitating the repetition of the data corrections from scratch. A recommended comprehensive sequence of elementary data correction steps is presented here to alleviate the difficulties associated with data correction, both in the laboratory and at the synchrotron. When applied in the proposed order to the raw signals, the resulting absolute scattering cross section will provide a high degree of accuracy for a very wide range of samples, with its values accompanied by uncertainty estimates. The method can be applied without modification to any pinhole-collimated instruments with photon-counting direct-detection area detectors.	Dec 2017
I22-Small angle scattering & Diffraction	Nanoparticle size distribution quantification: results of a small-angle X-ray scattering inter-laboratory comparison Brian R. Pauw , Claudia Kästner , Andreas F. Thünemann Journal Of Applied Crystallography 50, 1280 - 1288 DOI: 10.1107/S160057671701010X Open Access Show Abstract ▼ Abstract: This paper presents the first worldwide inter-laboratory comparison of small-angle X-ray scattering (SAXS) for nanoparticle sizing. The measurands in this comparison are the mean particle radius, the width of the size distribution and the particle concentration. The investigated sample consists of dispersed silver nanoparticles, surrounded by a stabilizing polymeric shell of poly(acrylic acid). The silver cores dominate the X-ray scattering pattern, leading to the determination of their radius size distribution using (i) the generalized indirect Fourier transformation method, (ii) classical model fitting using SASfit and (iii) a Monte Carlo fitting approach using McSAS. The application of these three methods to the collected data sets from the various laboratories produces consistent mean number- and volume-weighted core radii of Rn = 2.76 (6) nm and Rv = 3.20 (4) nm, respectively. The corresponding widths of the lognormal radius distribution of the particles were σn = 0.65 (1) nm and σv = 0.71 (1) nm. The particle concentration determined using this method was 3.0 (4) g l−1 or 4.2 (7) × 10−6 mol l−1. These results are affected slightly by the choice of data evaluation procedure, but not by the instruments: the participating laboratories at synchrotron SAXS beamlines, commercial and in-house-designed instruments were all able to provide highly consistent data. This demonstrates that SAXS is a suitable method for revealing particle size distributions in the sub-20 nm region (at minimum), out of reach for most other analytical methods.	Oct 2017
I22-Small angle scattering & Diffraction	Simultaneous SAXS and SANS analysis for the detection of toroidal supramolecular polymers composed of noncovalent supermacrocycles in solution Martin J. Hollamby , Keisuke Aratsu , B R. Pauw , Sarah Rogers , Andrew J. Smith , Mitsuaki Yamauchi , Xu Lin , Shiki Yagai Angewandte Chemie International Edition DOI: 10.1002/anie.201603370 Diamond Proposal Number(s): [11969] Show Abstract ▼ Abstract: Molecular self-assembly primarily occurs in solution. To better understand this process, techniques capable of probing the solvated state are consequently required. Small-angle scattering (SAS) has a proven ability to detect and characterize solutions, but it is rarely applied to more complex assembly shapes. Here, small-angle X-ray and neutron scattering are applied to observe toroidal assemblies in solution. Combined analysis confirms that the toroids have a core–shell structure, with a π-conjugated core and an alkyl shell into which solvent penetrates. The dimensions determined by SAS agree well with those obtained by (dried-state) atomic force microscopy. Increasing the number of naphthalene units in the molecular building block yields greater rigidity, as evidenced by a larger toroid and a reduction in solvent penetration into the shell. The detailed structural analysis demonstrates the applicability of SAS to monitor complex solution-based self-assembly.	Jul 2016
I22-Small angle scattering & Diffraction	Combined pressure and temperature denaturation of ribonuclease A produces alternate denatured states Timothy M. Ryan , Yun Xun , Nathan P. Cowieson , Jitendra P. Mata , Andrew Jackson , Brian R. Pauw , Andrew Smith , Nigel Kirby , Duncan Mcgillivray Biochemical And Biophysical Research Communications DOI: 10.1016/j.bbrc.2016.03.135 Show Abstract ▼ Abstract: Protein folding, unfolding and misfolding have become critically important to a range of health and industry applications. Increasing high temperature and high pressure are used to control and speed up reactions. A number of studies have indicated that these parameters can have a large ffect on protein structure and function. Here we describe the additive effects of these parameters on the small angle scattering behavior of ribonuclease A. We find that alternate unfolded structures can be obtained with combined high pressure and temperature treatment of the protein.	Mar 2016
I11-High Resolution Powder Diffraction	In situ synchrotron X-ray diffraction study of the sol-gel synthesis of Fe3N and Fe3C Zoe Schnepp , Ashleigh Danks , Martin Hollamby , Brian Pauw , Claire Murray , Chiu Tang Chemistry Of Materials 27 (14), 5094–5099 DOI: 10.1021/acs.chemmater.5b01811 Diamond Proposal Number(s): [9566] Show Abstract ▼ Abstract: Sol-gel chemistry is a powerful tool for the synthesis of porous or nanocrystalline structures of a wide range of materials. The morphology and composition of the final product can depend strongly on the mechanism that operates during the heating step, as has been demonstrated in many investigations of binary, ternary and quaternary metal oxides. We demonstrate the complex phase transformations occurring in a transition metal carbide (Fe3C, cementite) synthesis using in situ synchrotron X-ray diffraction. Our new study proves the existence of multiple intermediate phases and elucidates how oxide-nitride and nitride-carbide phase transformations can occur. This is particularly important as many transition metal nitrides and carbides are metastable, which renders their stability windows sensitive to small changes in sol-gel methodology	Jul 2015

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