On the Formation of Silicide Precipitates in Niobium-Silicide Based Composites

1998 ◽  
Vol 552 ◽  
Author(s):  
B. P. Bewlay ◽  
R. J. Grylls ◽  
H. L. Fraser
Keyword(s):  
Crystal Structure ◽  
Directional Solidification ◽  
Orientation Relationship ◽  
High Temperatures ◽  
Aircraft Engines ◽  
Orthorhombic Crystal ◽  
Detailed Characterization ◽  
Orthorhombic Crystal Structure ◽  
Very High

ABSTRACTComposites based on Nb-Si are attractive candidates for use as structural materials at the very high temperatures required for future aircraft engines. The composites described were produced by directional solidification, which gives a microstructure consisting of Nb dendrites with an Nb3Si-Nb eutectic. The aim of this paper is to provide a detailed characterization of precipitates observed in the Nb dendrites in both binary and higher-order alloys. The precipitates possess the Nb3Si stoichiometry, but not the stable Nb3Si structure. The precipitates form a metastable orthorhombic crystal structure which is related to the Nb matrix via a simple orientation relationship.

Effect of Strontium Doping Into CaBi2Nb2O9 Aurivillius Oxide Nanoceramics: Structural and Electrical Properties

2020 ◽  
Vol 15 (1) ◽  
pp. 32-40
Author(s):  
Ouissem Jalled ◽  
Mariah Alhassan ◽  
Seham R. Alharbi ◽  
Zaynab Alharbi ◽  
Yas Al-Hadeethi ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Sol Gel ◽  
Orthorhombic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Thermogravimetric Analyzer ◽  
Transmission Electron ◽  
Structural And Electrical Properties ◽  
Gel Combustion ◽  
Dielectric Constant Measurement

Herein, we report the synthesis and characterization of Ca1-xSrxBi2Nb2O9 (CSBNO) (0 ≤ x ≤ 1) nanoceramics prepared using sucrose-assisted sol–gel combustion methods. The synthesized nanoceramics were characterized by different tools like differential thermal and thermogravimetric analyzer (DTA-TG), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FTIR) spectrometer, X-ray powder diffraction (XRD), and impedance analyzer. DTA-TG reveals that the optimum temperature of calcination of CBN is higher than 1000 °C. The FTIR revealed the formation of CaBi2Nb2O9 (CBNO) at 614 cm-1. The XRD confirmed that all samples exhibited orthorhombic crystal structure. Increased orthorhombic distortion was spotted for doped CBNO and the structure acquires extra orthorhombicity through Sr doping. The TEM measurement inspected the increase of the grain size due to the inclusion of strontium into the orthorhombic crystal structure of CBNO from 56 nm to 76 nm. The dielectric constant measurement demonstrated that the increase in Sr content is associated with steady decrease in Curie temperature from 1207 K up to 720 K. The dielectric loss exhibited a minimum value at x = 0.5 and high stability along the temperature range of 300–850 K. Such property may enable this nanocomposite to be used for the application of FeRAM.

Spherulitic crystal growth in the prodissoconch larval of Crassostrea virginica

1983 ◽  
Vol 41 ◽  
pp. 518-519
Author(s):  
George G. Cocks ◽  
Louis Leibovitz ◽  
DoSuk D. Lee
Keyword(s):  
Crystal Structure ◽  
Crassostrea Virginica ◽  
Crystal Orientation ◽  
Developmental Changes ◽  
Gastrula Stage ◽  
Orthorhombic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Stages Of Growth ◽  
Early Stages ◽  
Initial Deposition

Our understanding of the structure and the formation of inorganic minerals in the bivalve shells has been considerably advanced by the use of electron microscope. However, very little is known about the ultrastructure of valves in the larval stage of the oysters. The present study examines the developmental changes which occur between the time of conception to the early stages of Dissoconch in the Crassostrea virginica(Gmelin), focusing on the initial deposition of inorganic crystals by the oysters.The spawning was induced by elevating the temperature of the seawater where the adult oysters were conditioned. The eggs and sperm were collected separately, then immediately mixed for the fertilizations to occur. Fertilized animals were kept in the incubator where various stages of development were stopped and observed. The detailed analysis of the early stages of growth showed that CaCO3 crystals(aragonite), with orthorhombic crystal structure, are deposited as early as gastrula stage(Figuresla-b). The next stage in development, the prodissoconch, revealed that the crystal orientation is in the form of spherulites.

scholarly journals Crystal Structures of New Ivermectin Pseudopolymorphs

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 172
Author(s):  
Kirill Shubin ◽  
Agris Bērziņš ◽  
Sergey Belyakov
Keyword(s):  
Crystal Structure ◽  
Molecular Conformation ◽  
Methyl Tert Butyl Ether ◽  
Minor Role ◽  
Scanning Calorimetry ◽  
Orthorhombic Crystal ◽  
Monoclinic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Space Group ◽  
Structure Space

New pseudopolymorphs of ivermectin (IVM), a potential anti-COVID-19 drug, were prepared. The crystal structure for three pseudopolymorphic crystalline forms of IVM has been determined using single-crystal X-ray crystallographic analysis. The molecular conformation of IVM in crystals has been compared with the conformation of isolated molecules modeled by DFT calculations. In a solvent with relatively small molecules (ethanol), IVM forms monoclinic crystal structure (space group I2), which contains two types of voids. When crystallized from solvents with larger molecules, like γ-valerolactone (GVL) and methyl tert-butyl ether (MTBE), IVM forms orthorhombic crystal structure (space group P212121). Calculations of the lattice energy indicate that interactions between IVM and solvents play a minor role; the main contribution to energy is made by the interactions between the molecules of IVM itself, which form a framework in the crystal structure. Interactions between IVM and molecules of solvents were evaluated using Hirshfeld surface analysis. Thermal analysis of the new pseudopolymorphs of IVM was performed by differential scanning calorimetry and thermogravimetric analysis.

scholarly journals Orthorhombic crystal structure and oxygen deficient cluster distribution model for YBa2Cu3−xAlxO6+δ superconductor

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
P. Manju ◽  
Neeraj K. Rajak ◽  
Andrews P. Alex ◽  
Vinayak B. Kamble ◽  
D. Jaiswal-Nagar
Keyword(s):  
Crystal Structure ◽  
Distribution Model ◽  
Orthorhombic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Cluster Distribution

scholarly journals (R)-Baclofen [(R)-4-amino-3-(4-chlorophenyl)butanoic acid]

2022 ◽  
Vol 78 (1) ◽  
Author(s):  
Feodor Belov ◽  
Alexander Villinger ◽  
Jan von Langermann
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Single Crystal ◽  
Title Compound ◽  
Single Crystal Xrd ◽  
Butanoic Acid ◽  
Orthorhombic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Space Group ◽  
Structure Space

This article provides the first single-crystal XRD-based structure of enantiopure (R)-baclofen (form C), C10H12ClNO2, without any co-crystallized substances. In the enantiopure title compound, the molecules arrange themselves in an orthorhombic crystal structure (space group P212121). In the crystal, strong hydrogen bonds and C—H ... Cl bonds interconnect the zwitterionic molecules.

Thermal enhancement of 2H11/2→4I15/2 up-conversion luminescence of Er3+ doped K2Yb(PO4)(MoO4) phosphors

2021 ◽  
Author(s):  
Hongqiang Cui ◽  
Yongze Cao ◽  
Lei Zhang ◽  
Yuhang Zhang ◽  
Siying Ran ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Solid State Reaction ◽  
Solid State Reaction Method ◽  
X Ray Diffraction ◽  
Orthorhombic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Reaction Method ◽  
X Ray ◽  
Thermal Enhancement

Er3+ with different concentrations doped K2Yb(PO4)(MoO4) phosphors were prepared by a solid-state reaction method, and the layered orthorhombic crystal structure of the samples was confirmed by X-ray diffraction (XRD). Under...

Size-dependent magnetic behavior and spin-wave gap in epitaxial films with orthorhombic crystal structure

2010 ◽  
Vol 322 (6) ◽  
pp. 664-667 ◽  
Author(s):  
I.V. Golosovsky ◽  
N.S. Sokolov ◽  
A. Gukasov ◽  
A. Bataille ◽  
M. Boehm ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Spin Wave ◽  
Magnetic Behavior ◽  
Epitaxial Films ◽  
Orthorhombic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Size Dependent ◽  
Spin Wave Gap

Orthorhombic crystal structure of the A-DNA octamer d(GTACGTAC). Comparison with the tetragonal structure

1993 ◽  
Vol 213 (2) ◽  
pp. 673-682 ◽  
Author(s):  
Beatrice LANGLOIS d'ESTAINTOT ◽  
Alain DAUTANT ◽  
Christian COURSEILLE ◽  
Gilles PRECIGOUX
Keyword(s):  
Crystal Structure ◽  
Tetragonal Structure ◽  
Orthorhombic Crystal ◽  
Orthorhombic Crystal Structure

Influence of Deposition Time on the Properties of Highly-Oriented SnS Thin Films Prepared Using the Thermal Evaporation Method

2012 ◽  
Vol 602-604 ◽  
pp. 1409-1412 ◽  
Author(s):  
Patrick. A. Nwofe ◽  
K. T. Ramakrishna Reddy ◽  
Robert W. Miles
Keyword(s):  
Crystal Structure ◽  
Single Phase ◽  
Deposition Time ◽  
Thermal Evaporation ◽  
Atomic Ratio ◽  
Energy Band Gap ◽  
Orthorhombic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Thermal Evaporation Method ◽  
Sns Thin Films

The influence of deposition time on the properties of SnS films grown using the thermal evaporation was reported. The deposition time was varied between 0.7 – 3 min, keeping other deposition variables constant. The layers showed single phase with orthorhombic crystal structure, exhibiting a strong (040) reflection. With an increase of deposition time, the Sn/S atomic ratio and grain size and the number of crystallites in the layers increased while the dislocation density and bulk resistivity decreased. The increase of crystallinity of the layers was confirmed by the change of strain from tensile to compressive with increasing deposition time. The transmittance of the films were > 70% for deposition time ≤ 1min and decreased drastically otherwise. The energy band gap varied in the range 1.80 - 1.30 eV with the lower values obtained at longer deposition times.

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