I15-1-X-ray Pair Distribution Function (XPDF)
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Diamond Proposal Number(s):
[18638]
Open Access
Abstract: Hydroxyapatite (HA) is a complex material, which is often nanocrystalline when found within a biological setting. This work has directly compared the structural characteristics derived from data collected using a conventional laboratory-based X-ray diffractometer with those collected from a dedicated pair distribution function (PDF) beamline at Diamond Light Source. In particular, the application of PDF analysis methods to carbonated HA is evaluated. 20 synthetic samples were measured using both X-ray diffraction (XRD) and PDFs. Both Rietveld refinement (of laboratory XRD data) and real-space refinement (of PDF data) were used to analyse all samples. The results of Rietveld and real-space refinements were compared to evaluate their application to crystalline and nanocrystalline hydroxyapatite. Significant relationships were observed between real-space refinement parameters and increasing carbonate substitution. Understanding the local order of synthetic hydroxyapatite can benefit several fields, including both biomedical and clinical settings.
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May 2022
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I15-1-X-ray Pair Distribution Function (XPDF)
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Diamond Proposal Number(s):
[22841]
Open Access
Abstract: The effect of substituting Cu by elemental additions of Ni or Co on the atomic structure of the Zr60Cu30Al10 ternary bulk metallic glass (BMG) is studied using high-energy synchrotron radiation X-ray diffraction. Analyses of the structural features in reciprocal and real space using the structure factors S(Q) and pair-distribution functions (PDF) point to an increase in the structural disorder for the Ni- or Co-bearing quaternary alloys. This is consistent with the “confusion principle” since upon alloying the initially nearly identical atomic sizes of Cu, Ni and Co diversify due to local electronic interactions. In real space, the disordering is manifested by a reduced deviation from the average particle density visible in the nearest-neighbour (NN) atomic shell structure over the complete short- and medium-range order region. Despite their similar atomic size, enthalpies of mixing with the main alloy elements and apparent disordering of the structure, the additions of Ni or Co have different effects on thermal stability of the ternary “mother” alloy.
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Apr 2022
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I15-1-X-ray Pair Distribution Function (XPDF)
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Jette K.
Mathiesen
,
Espen D.
Bøjesen
,
Jack K.
Pedersen
,
Emil T. S.
Kjær
,
Mikkel
Juelsholt
,
Susan
Cooper
,
Jonathan
Quinson
,
Andy S.
Anker
,
Geoff
Cutts
,
Dean S.
Keeble
,
Maria S.
Thomsen
,
Jan
Rossmeisl
,
Kirsten M. Ø.
Jensen
Diamond Proposal Number(s):
[20187]
Open Access
Abstract: Intermetallic nanoparticles (NPs) have shown enhanced catalytic properties as compared to their disordered alloy counterparts. To advance their use in green energy, it is crucial to understand what controls the formation of intermetallic NPs over alloy structures. By carefully selecting the additives used in NP synthesis, it is here shown that monodisperse, intermetallic PdCu NPs can be synthesized in a controllable manner. Introducing the additives iron(III) chloride and ascorbic acid, both morphological and structural control can be achieved. Combined, these additives provide a synergetic effect resulting in precursor reduction and defect-free growth; ultimately leading to monodisperse, single-crystalline, intermetallic PdCu NPs. Using in situ X-ray total scattering, a hitherto unknown transformation pathway is reported that diverges from the commonly reported coreduction disorder–order transformation. A Cu-rich structure initially forms, which upon the incorporation of Pd(0) and atomic ordering forms intermetallic PdCu NPs. These findings underpin that formation of stoichiometric intermetallic NPs is not limited by standard reduction potential matching and coreduction mechanisms, but is instead driven by changes in the local chemistry. Ultimately, using the local chemistry as a handle to tune the NP structure might open new opportunities to expand the library of intermetallic NPs by exploiting synthesis by design.
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Apr 2022
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I15-1-X-ray Pair Distribution Function (XPDF)
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Alice M.
Bumstead
,
Ignas
Pakamore
,
Kieran D.
Richards
,
Michael F.
Thorne
,
Sophia S.
Boyadjieva
,
Celia
Castillo-Blas
,
Lauren N.
Mchugh
,
Adam F.
Sapnik
,
Dean S.
Keeble
,
David A.
Keen
,
Rachel C.
Evans
,
Ross S.
Forgan
,
Thomas D.
Bennett
Diamond Proposal Number(s):
[20038]
Abstract: Melt-quenched metal–organic framework (MOF) glasses have gained significant interest as the first new category of glass reported in 50 years. In this work, an amine-functionalized zeolitic imidazolate framework (ZIF), denoted ZIF-UC-6, was prepared and demonstrated to undergo both melting and glass formation. The presence of an amine group resulted in a lower melting temperature compared to other ZIFs, while also allowing material properties to be tuned by post-synthetic modification (PSM). As a prototypical example, the ZIF glass surface was functionalized with octyl isocyanate, changing its behavior from hydrophilic to hydrophobic. PSM therefore provides a promising strategy for tuning the surface properties of MOF glasses.
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Feb 2022
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I15-1-X-ray Pair Distribution Function (XPDF)
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Diamond Proposal Number(s):
[18630]
Open Access
Abstract: The structures of Zr and Hf metal–organic frameworks (MOFs) are very sensitive to small changes in synthetic conditions. One key difference affecting the structure of UiO MOF phases is the shape and nuclearity of Zr or Hf metal clusters acting as nodes in the framework; although these clusters are crucial, their evolution during MOF synthesis is not fully understood. In this paper, we explore the nature of Hf metal clusters that form in different reaction solutions, including in a mixture of DMF, formic acid, and water. We show that the choice of solvent and reaction temperature in UiO MOF syntheses determines the cluster identity and hence the MOF structure. Using in situ X-ray pair distribution function measurements, we demonstrate that the evolution of different Hf cluster species can be tracked during UiO MOF synthesis, from solution stages to the full crystalline framework, and use our understanding to propose a formation mechanism for the hcp UiO-66(Hf) MOF, in which first the metal clusters aggregate from the M6 cluster (as in fcu UiO-66) to the hcp-characteristic M12 double cluster and, following this, the crystalline hcp framework forms. These insights pave the way toward rationally designing syntheses of as-yet unknown MOF structures, via tuning the synthesis conditions to select different cluster species.
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Nov 2021
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I15-1-X-ray Pair Distribution Function (XPDF)
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Diamond Proposal Number(s):
[20038]
Open Access
Abstract: Zeolitic imidazolate frameworks (ZIFs) can be melt-quenched to form glasses. Here, we present an alternative route to glassy ZIFs via mechanically induced amorphisation. This approach allows various glassy ZIFs to be produced in under 30 minutes at room temperature, without the need for melt-quenching.
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Aug 2021
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I15-1-X-ray Pair Distribution Function (XPDF)
I15-Extreme Conditions
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Diamond Proposal Number(s):
[17785, 13681]
Abstract: Hard carbons are the leading candidate anode materials for sodium-ion batteries. However, the sodium-insertion mechanisms remain under debate. Here, employing a novel analysis of operando and ex situ pair distribution function (PDF) analysis of total scattering data, supplemented by information on the local electronic structure provided by operando 23Na solid-state NMR, we identify the local atomic environments of sodium stored within hard carbon and provide a revised mechanism for sodium storage. The local structure of carbons is well-described by bilayers of curved graphene fragments, with fragment size increasing, and curvature decreasing with increasing pyrolysis temperature. A correlation is observed between the higher-voltage (slope) capacity and the defect concentration inferred from the size and curvature of the fragments. Meanwhile, a larger lower-voltage (plateau) capacity is observed in samples modeled by larger fragment sizes. Operando PDF data on two commercially relevant hard carbons reveal changes at higher-voltages consistent with sodium ions stored close to defective areas of the carbon, with electrons localized in the antibonding π*-orbitals of the carbon. Metallic sodium clusters approximately 13–15 Å in diameter are formed in both carbons at lower voltages, implying that, for these carbons, the lower-voltage capacity is determined by the number of regions suitable for sodium cluster formation, rather than by having microstructures that allow larger clusters to form. Our results reveal that local atomic structure has a definitive role in determining storage capacity, and therefore the effect of synthetic conditions on both the local atomic structure and the microstructure should be considered when engineering hard carbons.
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Aug 2021
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I15-1-X-ray Pair Distribution Function (XPDF)
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Diamond Proposal Number(s):
[15959]
Open Access
Abstract: The sol–gel synthesis of iron carbide (Fe3C) nanoparticles proceeds through multiple intermediate crystalline phases, including iron oxide (FeOx) and iron nitride (Fe3N). The control of particle size is challenging, and most methods produce polydisperse Fe3C nanoparticles of 20–100 nm in diameter. Given the wide range of applications of Fe3C nanoparticles, it is essential that we understand the evolution of the system during the synthesis. Here, we report an in situ synchrotron total scattering study of the formation of Fe3C from gelatin and iron nitrate sol–gel precursors. A pair distribution function analysis reveals a dramatic increase in local ordering between 300 and 350 °C, indicating rapid nucleation and growth of iron oxide nanoparticles. The oxide intermediate remains stable until the emergence of Fe3N at 600 °C. Structural refinement of the high-temperature data revealed local distortion of the NFe6 octahedra, resulting in a change in the twist angle suggestive of a carbonitride intermediate. This work demonstrates the importance of intermediate phases in controlling the particle size of a sol–gel product. It is also, to the best of our knowledge, the first example of in situ total scattering analysis of a sol–gel system.
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May 2021
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I15-1-X-ray Pair Distribution Function (XPDF)
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Bikash Kumar
Shaw
,
Ashlea R.
Hughes
,
Maxime
Ducamp
,
Stephen
Moss
,
Anup
Debnath
,
Adam F.
Sapnik
,
Michael F.
Thorne
,
Lauren N.
Mchugh
,
Andrea
Pugliese
,
Dean S.
Keeble
,
Philip
Chater
,
Juan M.
Bermudez-Garcia
,
Xavier
Moya
,
Shyamal K.
Saha
,
David A.
Keen
,
François-Xavier
Coudert
,
Frédéric
Blanc
,
Thomas
Bennett
Diamond Proposal Number(s):
[20038]
Abstract: Several organic–inorganic hybrid materials from the metal–organic framework (MOF) family have been shown to form stable liquids at high temperatures. Quenching then results in the formation of melt-quenched MOF glasses that retain the three-dimensional coordination bonding of the crystalline phase. These hybrid glasses have intriguing properties and could find practical applications, yet the melt-quench phenomenon has so far remained limited to a few MOF structures. Here we turn to hybrid organic–inorganic perovskites—which occupy a prominent position within materials chemistry owing to their functional properties such as ion transport, photoconductivity, ferroelectricity and multiferroicity—and show that a series of dicyanamide-based hybrid organic–inorganic perovskites undergo melting. Our combined experimental–computational approach demonstrates that, on quenching, they form glasses that largely retain their solid-state inorganic–organic connectivity. The resulting materials show very low thermal conductivities (~0.2 W m−1 K−1), moderate electrical conductivities (10−3–10−5 S m−1) and polymer-like thermomechanical properties.
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May 2021
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E02-JEM ARM 300CF
I15-1-X-ray Pair Distribution Function (XPDF)
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Adam F.
Sapnik
,
Duncan N.
Johnstone
,
Sean M.
Collins
,
Giorgio
Divitini
,
Alice M.
Bumstead
,
Christopher W.
Ashling
,
Philip A.
Chater
,
Dean S.
Keeble
,
Timothy
Johnson
,
David A.
Keen
,
Thomas D.
Bennett
Diamond Proposal Number(s):
[20038, 20198]
Open Access
Abstract: Defect engineering is a powerful tool that can be used to tailor the properties of metal–organic frameworks (MOFs). Here, we incorporate defects through ball milling to systematically vary the porosity of the giant pore MOF, MIL-100 (Fe). We show that milling leads to the breaking of metal–linker bonds, generating additional coordinatively unsaturated metal sites, and ultimately causes amorphisation. Pair distribution function analysis shows the hierarchical local structure is partially retained, even in the amorphised material. We find that solvents can be used to stabilise the MIL-100 (Fe) framework against collapse, which leads to a substantial retention of porosity over the non-stabilised material.
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Mar 2021
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