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  • 1
    Online Resource
    Online Resource
    International Union of Crystallography (IUCr) ; 2021
    In:  Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials Vol. 77, No. 6 ( 2021-12-01), p. 986-995
    In: Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials, International Union of Crystallography (IUCr), Vol. 77, No. 6 ( 2021-12-01), p. 986-995
    Abstract: A new six-membered cyclic alkanolamine with chemical formula C 6 H 15 N 3 O 3 was synthesized by the reaction of glycolaldehyde with gaseous ammonia. The molecular structure, characterized by a hexagonal ring of alternating carbon and nitrogen atoms with three hydroxymethyl groups attached to the carbon atoms, could not be unambiguously determined by elemental analysis and 1 H/ 13 C/ 15 N NMR. The molecular structure and conformation were further determined using a combination of vibrational spectroscopy (IR and Raman) and real-space pair distribution function (PDF) analysis. The crystal structure was determined ab initio from laboratory X-ray powder diffraction (XRPD) with orthorhombic space group Ama 2 (No. 40) and unit-cell parameters a = 12.1054 (2) Å, b = 13.5537 (2) Å and c = 5.20741 (8) Å. Consistent structure models could be obtained by symmetry-independent PDF and PDF-Rietveld co-refinements. Independent local structure refinements indicate that the most likely deviations from the average structure consist of small tilting and translational distortions of hydrogen-bonded molecular stacks. Thermal analysis (TG/DTA) and temperature-dependent XRPD measurements were also performed to determine the thermal behavior.
    Type of Medium: Online Resource
    ISSN: 2052-5206
    Language: Unknown
    Publisher: International Union of Crystallography (IUCr)
    Publication Date: 2021
    detail.hit.zdb_id: 2020841-8
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  • 2
    Online Resource
    Online Resource
    African Journals Online (AJOL) ; 2021
    In:  Tanzania Journal of Science Vol. 47, No. 4 ( 2021-10-28), p. 1362-1375
    In: Tanzania Journal of Science, African Journals Online (AJOL), Vol. 47, No. 4 ( 2021-10-28), p. 1362-1375
    Abstract: Mesoporous carbon has been synthesized by activating carbonized biogas slurry residues with ZnCl2 and KOH simultaneously. The carbon to activating agent mass ratios were kept at 1:4, while the ZnCl2 to KOH mass ratio varied from 4:0, 3:1, 2:2, 1:3, to 0:4. The highest BET specific surface area of 361 m2 g-1, micropore surface area of 231 m2 g‒1, mesopore surface area of 125 m2 g‒1, and total pore volume of 0.23 cm3 g‒1 which amounted to 78% mesopore content, were obtained for the sample with 3:1 ZnCl2 to KOH mass ratio. Scanning electron microscope (SEM) images were acquired to determine the surface morphology and energy dispersive X-ray (EDX) was used to determine surface composition of the samples. The short, medium, and long-range orders of the synthesized materials were studied using pair distribution function (PDF) analysis. PDF showed that in addition to the locally ordered carbon and silica phase components, samples activated using combined ZnCl2 and KOH also contained crystalline Zn2SiO4 phase with the willemite structure. Electrochemical studies in three-electrode cell system revealed maximum specific capacitance of 216 F g‒1 exhibited by sample with a ZnCl2: KOH mass ratio of 3:1 at a scan rate of 5 mV s‒1. Keywords: Mesoporous carbon; Pair distribution function, Specific capacitance, supercapacitor  
    Type of Medium: Online Resource
    ISSN: 2507-7961 , 0856-1761
    Language: Unknown
    Publisher: African Journals Online (AJOL)
    Publication Date: 2021
    detail.hit.zdb_id: 2641763-7
    SSG: 11
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  • 3
    Online Resource
    Online Resource
    International Union of Crystallography (IUCr) ; 2019
    In:  Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials Vol. 75, No. 4 ( 2019-08-01), p. 532-549
    In: Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials, International Union of Crystallography (IUCr), Vol. 75, No. 4 ( 2019-08-01), p. 532-549
    Abstract: The pair distribution function (PDF) is a versatile tool to describe the structure of disordered and amorphous materials. Electron PDF (ePDF) uses the advantage of strong scattering of electrons, thus allowing small volumes to be probed and providing unique information on structure variations at the nano-scale. The spectrum of ePDF applications is rather broad: from ceramic to metallic glasses and mineralogical to organic samples. The quantitative interpretation of ePDF relies on knowledge of how structural and instrumental effects contribute to the experimental data. Here, a broad overview is given on the development of ePDF as a structure analysis method and its applications to diverse materials. Then the physical meaning of the PDF is explained and its use is demonstrated with several examples. Special features of electron scattering regarding the PDF calculations are discussed. A quantitative approach to ePDF data treatment is demonstrated using different refinement software programs for a nanocrystalline anatase sample. Finally, a list of available software packages for ePDF calculation is provided.
    Type of Medium: Online Resource
    ISSN: 2052-5206
    Language: Unknown
    Publisher: International Union of Crystallography (IUCr)
    Publication Date: 2019
    detail.hit.zdb_id: 2020841-8
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  • 4
    Online Resource
    Online Resource
    International Union of Crystallography (IUCr) ; 2017
    In:  Journal of Applied Crystallography Vol. 50, No. 3 ( 2017-06-01), p. 741-748
    In: Journal of Applied Crystallography, International Union of Crystallography (IUCr), Vol. 50, No. 3 ( 2017-06-01), p. 741-748
    Abstract: The particle size of supported catalysts is a key characteristic for determining structure–property relationships. It is a challenge to obtain this information accurately and in situ using crystallographic methods owing to the small size of such particles ( 〈 5 nm) and the fact that they are supported. In this work, the pair distribution function (PDF) technique was used to obtain the particle size distribution of supported Pt catalysts as they grow under typical synthesis conditions. The PDF of Pt nanoparticles grown on zeolite X was isolated and refined using two models: a monodisperse spherical model (single particle size) and a lognormal size distribution. The results were compared and validated using scanning transmission electron microscopy (STEM) results. Both models describe the same trends in average particle size with temperature, but the results of the number-weighted lognormal size distributions can also accurately describe the mean size and the width of the size distributions obtained from STEM. Since the PDF yields crystallite sizes, these results suggest that the grown Pt nanoparticles are monocrystalline. This work shows that refinement of the PDF of small supported monocrystalline nanoparticles can yield accurate mean particle sizes and distributions.
    Type of Medium: Online Resource
    ISSN: 1600-5767
    Language: Unknown
    Publisher: International Union of Crystallography (IUCr)
    Publication Date: 2017
    detail.hit.zdb_id: 2020879-0
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  • 5
    Online Resource
    Online Resource
    International Union of Crystallography (IUCr) ; 2020
    In:  Acta Crystallographica Section A Foundations and Advances Vol. 76, No. 3 ( 2020-05-01), p. 395-409
    In: Acta Crystallographica Section A Foundations and Advances, International Union of Crystallography (IUCr), Vol. 76, No. 3 ( 2020-05-01), p. 395-409
    Abstract: A new approach is presented to obtain candidate structures from atomic pair distribution function (PDF) data in a highly automated way. It fetches, from web-based structural databases, all the structures meeting the experimenter's search criteria and performs structure refinements on them without human intervention. It supports both X-ray and neutron PDFs. Tests on various material systems show the effectiveness and robustness of the algorithm in finding the correct atomic crystal structure. It works on crystalline and nanocrystalline materials including complex oxide nanoparticles and nanowires, low-symmetry and locally distorted structures, and complicated doped and magnetic materials. This approach could greatly reduce the traditional structure searching work and enable the possibility of high-throughput real-time auto-analysis PDF experiments in the future.
    Type of Medium: Online Resource
    ISSN: 2053-2733
    Language: Unknown
    Publisher: International Union of Crystallography (IUCr)
    Publication Date: 2020
    detail.hit.zdb_id: 2020844-3
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  • 6
    Online Resource
    Online Resource
    International Union of Crystallography (IUCr) ; 2021
    In:  Acta Crystallographica Section A Foundations and Advances Vol. 77, No. a2 ( 2021-08-14), p. C498-C498
    In: Acta Crystallographica Section A Foundations and Advances, International Union of Crystallography (IUCr), Vol. 77, No. a2 ( 2021-08-14), p. C498-C498
    Type of Medium: Online Resource
    ISSN: 2053-2733
    Language: Unknown
    Publisher: International Union of Crystallography (IUCr)
    Publication Date: 2021
    detail.hit.zdb_id: 2020844-3
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