1. Infrared spectra in amorphous alumina: A combined ab initio and experimental studyLuigi Giacomazzi, Nikita S. Shcheblanov, Mikhail E. Povarnitsyn, Yanbo Li, Andraž Mavrič, Barbara Zupančič, Jože Grdadolnik, Alfredo Pasquarello, 2023, original scientific article Abstract: We present a combined study based on the experimental measurements of an infrared (IR) dielectric function and first-principles calculations of IR spectra and the vibrational density of states (VDOS) of amorphous alumina (am−Al2O3). In particular, we show that the main features of the imaginary part of the dielectric function ε2(ω) at ∼380 and 630 cm−1 are related to the motions of threefold-coordinated oxygen atoms, which are the vast majority of oxygen atoms in am-Al2O3. Our analysis provides an alternative point of view with respect to an earlier suggested assignment of the vibrational modes, which relates them to the stretching and bending vibrational modes of AlOn (n=4, 5, and 6) polyhedra. Our assignment is based on the additive decomposition of the VDOS and ε2(ω) spectra, which shows that (i) the band at ∼380cm−1 features oxygen motions occurring in a direction normal to the plane defined by the three nearest-neighbor aluminum atoms, i.e., out-of-plane motions of oxygen atoms; (ii) Al-O stretching vibrations (i.e., in-plane motions of oxygen atoms) appear at frequencies above ∼500cm−1, which characterize the vibrational modes underlying the band at ∼630cm−1. Aluminum and fourfold-coordinated oxygen atoms contribute uniformly to the VDOS and ε2(ω) spectra in the frequency region ∼350–650 cm−1 without causing specific features. Our numerical results are in good agreement with the previous and presently obtained experimental data on the IR dielectric function of am−Al2O3 films. Finally, we show that the IR spectrum can be modeled successfully by assuming isotropic Born charges for aluminum atoms and fourfold-coordinated oxygen atoms, while requiring the use of three parameters, defined in a local reference frame, for the anisotropic Born charges of threefold-coordinated oxygen atoms.
Keywords: Dielectric properties, Microstructure, Amorphous materials, Density functional calculations, Infrared techniques, aluminium oxide
Published in RUNG: 10.05.2023; Views: 129; Downloads: 2
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2. Improved photopyroelectric (PPE) configuration for thermal effusivity investigations of porous solidsCarmen Tripon, Mohanachandran Nair Sindhu Swapna, Nicoleta Cobirzan, Dorota Korte, Robert Gutt, Marcel Bojan, Mladen Franko, Dorin Dadarlat, 2023, original scientific article Keywords: photothermal techniques, photopyroelectric calorimetry, thermal effusivity, porous solids, building materials
Published in RUNG: 12.04.2023; Views: 200; Downloads: 14
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3. Solution-processed graphene-nanographene van der Waals heterostructures for photodetectors with efficient and ultralong charge separationZhaoyang Liu, Haixin Qiu, Shuai Fu, Can Wang, Xuelin Yao, Alex Dixon, Stéphane Campidelli, Egon Pavlica, Gvido Bratina, Sheng Zhao, Loïc Rondin, 2021, original scientific article Keywords: absorption, colloids, molecules, sensors, two dimensional materials
Published in RUNG: 28.02.2023; Views: 244; Downloads: 0 |
4. Salicylaldehydate coordinated two-dimensional-conjugated metal–organic frameworksAbdul Khayum Mohammed, Pilar Pena-Sanchez, Ajmal Pandikassala, Safa Gaber, Ayesha A. AlKhoori, Tina Skorjanc, Kyriaki Polychronopoulou, Sreekumar Kurungot, Felipe Gandara, Dinesh Shetty, 2023, original scientific article Keywords: metal-organic framework, 2D materials, salicylaldehyde, thin films, mechanochemistry
Published in RUNG: 10.02.2023; Views: 246; Downloads: 0
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6. Hydrophobicity Tuning in Isostructural Urchin-Shaped Covalent Organic Framework Nanoparticles by Pore Surface Engineering for Oil–Water SeparationGobinda Das, Tina Skorjanc, Thirumurugan Prakasam, Bikash Garai, Salma Abubakar, Christina Zalch Saad, Felipe Gandara, Renu Pasricha, Sudhir Kumar Sharma, Sabu Varghese, Ramesh Jagannathan, Mark A. Olson, Ali Trabolsi, 2022, original scientific article Keywords: Adsorption, Covalent organic frameworks, Hydrophobicity, Lipids, Materials
Published in RUNG: 26.09.2022; Views: 461; Downloads: 0
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7. Polythiacalixarene-embedded gold nanoparticles for visible-light-driven photocatalytic CO [sub] 2 reductionTina Škorjanc, Kamal Khaja Mohaideen, Ayesha Alkhoori, Gregor Mali, Abdul Khayum Mohammed, Zouhair Asfari, Kyriaki Polychronopoulou, Blaž Likozar, Ali Trabolsi, Dinesh Shetty, 2022, original scientific article Keywords: Gold, Materials, Metal nanoparticles, Photocatalysis, Polymers
Published in RUNG: 13.07.2022; Views: 611; Downloads: 0
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10. Natural precursor based hydrothermal synthesis of sodium carbide for reactor applicationsSwapna Mohanachandran Nair Sindhu, 2017, original scientific article Abstract: Carbides are a class of materials with high mechanical strength and refractory nature which finds a wide range of applications in industries and nuclear reactors. The existing synthesis methods of all types of carbides have problems in terms of use of toxic chemical precursors, high-cost, etc. Sodium carbide (Na2C2) which is an alkali metal carbide is the least explored one and also that there is no report of low-cost and low-temperature synthesis of sodium carbide using the eco-friendly, easily available natural precursors. In the present work, we report a simple low-cost, non-toxic hydrothermal synthesis of refractory sodium carbide using the natural precursor—Pandanus. The formation of sodium carbide along with boron carbide is evidenced by the structural and morphological characterizations. The sample thus synthesized is subjected to field emission scanning electron microscopy (FESEM), x-ray powder diffraction (XRD), ultraviolet (UV)—visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), Raman, and photoluminescent (PL) spectroscopic techniques.
Keywords: sodium carbide, pandanus, hydrothermal synthesis, porous materials
Published in RUNG: 30.06.2022; Views: 532; Downloads: 0
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