Influence of modifier cations on the local environment of aluminum in La2O3–Al2O3 and Y2O3–Al2O3 binary glasses

2020 ◽  
Vol 22 (35) ◽  
pp. 19592-19599
Author(s):  
Yasuhiro Watanabe ◽  
Atsunobu Masuno ◽  
Hiroyuki Inoue ◽  
Yutaka Yanaba ◽  
Katsuyoshi Kato

In aluminate glasses, the oxygen coordination number around Al depends mainly on packing density.

2021 ◽  
Vol 129 (4) ◽  
pp. 527
Author(s):  
Afrash Ejigu A ◽  
K.P. Ramesh ◽  
Gajanan Honnavar

In this communication, we report physical and thermal properties along with Raman spectroscopic investigations on Zinc Niobo Tellurite glass systems doped with Eu2O3 and Dy2O3 at the expense of TeO2. The glasses have been synthesized by the melt quenching technique. Physical parameters like density, molar volume, packing density were estimated. The density of the un-doped glasses increases with increasing mol% of the modifier (ZnO) whereas the glass transition temperature (Tg) decreases. We have observed an increase in the density of the base glass systems which are doped with rare earth (RE) dopants. The packing density of the un-doped glasses remains almost constant with increasing modifier content suggesting that there is not much change in the local environment. Raman spectra were recorded at room temperature and assigned to TeO4 and TeO3 structural units in these glasses. The peak shift, full width at half maximum (FWHM) of the de-convoluted Raman peaks were analyzed to get information about the local environment. It is observed that these compositions of tellurite glasses are good host materials for rare earth ions as they offer voids in the network. Further, it was observed that the rare earth ion doping has not affected the local environment of the glasses; Dy3+ ions have a slightly higher tendency to polarize Te-O bonds than the Eu3+ ions. Keywords: Niobium-based tellurite glasses, XRD, DSC, FTIR.


2013 ◽  
Vol 1518 ◽  
pp. 59-64 ◽  
Author(s):  
S.V. Stefanovsky ◽  
A.A. Shiryaev ◽  
Y.V. Zubavichus ◽  
K.M. Fox ◽  
J.C. Marra

ABSTRACTValence state and local environment of Fe in complex glasses related to the system Al2O3-B2O3-Fe2O3-Na2O-SiO2 were studied. In all the glasses, the major fraction of Fe exists as Fe3+ ions but a minor fraction of Fe2+ ions especially in the glass with the lowest K=[SiO2]/[B2O3] ratio was also present. Average Fe—O distance in the first shell is 1.80-1.85 Å and coordination number is 4-6. The intensity due to the second sphere is rather weak demonstrating homogeneous distribution of Fe ions in the glass.


1976 ◽  
Vol 40 (5) ◽  
pp. 480-486 ◽  
Author(s):  
Kenji Morinaga ◽  
Yukio Suginohara ◽  
Tsutomu Yanagase

Author(s):  
Raihan Tayeb ◽  
Xin Dou ◽  
Yijin Mao ◽  
Yuwen Zhang

Granular packing structures of cohesive microsized particles with different sizes and size distributions, including monosized, uniform, and Gaussian distribution, are investigated by using two different history dependent contact models with discrete element method (DEM). The simulation is carried out in the framework of liggghts, which is a DEM simulation package extended based on branch of granular package of widely used open-source code LAMMPS. Contact force caused by translation and rotation, frictional and damping forces due to collision with other particles or container boundaries, cohesive force, van der Waals force, and gravity is considered. The radial distribution functions (RDFs), force distributions, porosities, and coordination numbers under cohesive and noncohesive conditions are reported. The results indicate that particle size and size distributions have great influences on the packing density for particle packing under cohesive effect: particles with Gaussian distribution have the lowest packing density, followed by the particles with uniform distribution; the particles with monosized distribution have the highest packing density. It is also found that cohesive effect to the system does not significantly affect the coordination number that mainly depends on the particle size and size distribution. Although the magnitude of net force distribution is different, the results for porosity, coordination number, and mean value of magnitude of net force do not vary significantly between the two contact models.


1972 ◽  
Vol 27 (6) ◽  
pp. 1022-1024 ◽  
Author(s):  
S. Haussühl ◽  
R. Leckebusch ◽  
K. Recker

AbstractThe elastic and thermoelastic constants of cubic LiBaF3 are measured by ultrasonic methods. As a consequence of the larger packing density which results from the higher coordination number of the Ba ions in LiBaF3 the values for the mean elastic stiffness and for the refractive index exceed those of LiF and BaF2 . A quantitative explanation of these properties is given. The values of many other properties range between those of LiF and BaF2.


1993 ◽  
Vol 57 (389) ◽  
pp. 671-676 ◽  
Author(s):  
Simona Quartieri ◽  
Gilberto Artioli ◽  
Antonio Deriu ◽  
Pier Paolo Lottici ◽  
Gianni Antonioli

AbstractA Mössbauer investigation has been carried out on garnets from the Ivrea-Verbano zone and the results are compared with those obtained on the same samples by X-ray absorption spectroscopy (XAS). The problem addressed is the precise structural characterisation of the local environment of iron in garnets with Fe/Ca ratio variable between ∼3.0 and ∼18.0. Ferric iron is octahedrally coordinated and ferrous iron is in the dodecahedral site in all the samples. Mössbauer results are in agreement with those obtained by XAS and show that, at least in the compositional range of the garnets examined (0.1-0.5 calcium atoms p.f.u.), the iron environment is not significantly modified by the larger calcium cations sharing the same dodecahedral site. It is confirmed that the Mössbauer technique is more sensitive than XAS in detecting low percentages of iron, especially when the cation is present in more than one oxidation state and coordination number.


2014 ◽  
Vol 386 ◽  
pp. 56-60 ◽  
Author(s):  
Oliver L.G. Alderman ◽  
Alex C. Hannon ◽  
Diane Holland ◽  
Norimasa Umesaki

Author(s):  
Zhaowei Xiang ◽  
Ming Yin ◽  
Zhenbo Deng ◽  
Xiaoqin Mei ◽  
Guofu Yin

The forming process of powder bed for additive manufacturing (AM) is analyzed and is simplified to three processes, including random packing, layering, and compression. The processes are simulated by using the discrete element method (DEM). First, the particles with monosize, bimodal, and Gaussian size distributions are randomly packed. Then, the packed particles are layered with different thicknesses. Finally, a 20 μm compression is applied on the top surface of the layered powder beds. All the processes are simulated based on the soft sphere model. Packing density and coordination number are calculated to evaluate the packing mesostructure. The results indicate that the packing density and coordination number increase with the layer thickness increasing in the initial packing, and compression can effectively increase the density and coordination number of powder bed and decrease the effect of ranging layer thickness. The results also show that powder bed with monosize distribution initially has the best combination performance. Our research provides a theoretical guide to choosing the layer thickness and size distribution initially of powder bed for AM.


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