scholarly journals Avoiding or Promoting Graphite in Carbon-Rich Chromium-Containing CoNiFer Cast Alloys—Part 2: Microstructures of the Elaborated Alloys

2012 ◽  
Vol 2012 ◽  
pp. 1-7
Author(s):  
Ophélie Hestin ◽  
Elise Souaillat ◽  
Ahmed Dia ◽  
Moussa Ba ◽  
Patrice Berthod
Keyword(s):  
Ternary Alloys ◽  
Chemical Compositions ◽  
X Ray Diffraction ◽  
Graphite Phase ◽  
X Ray ◽  
Microscopy Image ◽  
Cast Alloys ◽  
The Mean ◽  
Microscopy Image Analysis ◽  
Good Agreement

Nine M-xCr-yC ternary alloys, three cobalt based, three nickel based and three iron based, were elaborated by foundry, from chemical compositions previously selected by the mean of thermodynamic calculations. They were metallographically characterized, using electron microscopy, image analysis, and X-ray diffraction. The as-cast microstructures are in rather good agreement with the ones predicted at 500 and/or 600°C, despite that the elaboration conditions did not meet any thermodynamic equilibrium criteria. Indeed, the obtained carbides and graphite fractions were close to the calculated ones, and the new chromium contents previously chosen effectively led to the expected microstructure modifications, notably almost total suppression of graphite in the nickel alloys and obtaining large fractions of carbides in the cobalt alloys. This allowed specifying the hardness evolution resulting, for these alloys, from the presence or absence of the soft graphite phase, and from the lowering or the enhancement of the carbides presence.

Nickel-containing montmorillonites and chlorites from Brazil, with remarks on schuchardtite

1975 ◽  
Vol 40 (310) ◽  
pp. 141-152 ◽  
Author(s):  
G. W. Brindley ◽  
Jefferson V. De Souza
Keyword(s):  
Structural Formula ◽  
Layer Charge ◽  
Basal Spacing ◽  
Chemical Compositions ◽  
X Ray Diffraction ◽  
Octahedral Sheet ◽  
X Ray ◽  
Crystalline Forms ◽  
Polytype Structure ◽  
Good Agreement

SummaryClay-like, hydrous nickel silicates from Niquelandia, Goias, Brazil, and from Jacupiranga, São Paulo, Brazil, arc examined by X-ray diffraction, chemical analysis, and thermogravimetric methods. The nickel silicates from Niquelandia are ferric iron montmorillonites, with nickel in the octahedral positions and, to a lesser extent, in interlayer positions. The chemical compositions of samples dried at 110°C average (Mg0.15Ni0.08Ca0.015Na0.005) (Fe0.92IIIFe0.025IIAl0.55Mg0.37Ni0.22) (Si3.88Al0.12)O10(OH)2(H2O)0.93. The layer charge originates largely in the octahedral sheet. The cation-exchange capacities average 107 me/100 g clay (110°C). These minerals differ from non-tronites, in which the layer charge originates mainly in the tetrahedral sheets.The nickel silicates from Jacupiranga resemble chlorites, with a non-expanding basal spacing of 14·2-14·3 Å. The better crystalline forms give X-ray data in good agreement with a la polytype structure, which is consistent with their formation by low-temperature processes. Chemical formulae derived on the basis of O10(OH)8 give an average of 5·47 cations in octahedral positions. Thermogravimetric measurements show up to 4% H2O lost between 110 and 500 °C. These results suggest a partial vermiculitization of the interlayer sheets. A new method of calculating a structural formula is developed that gives an interlayer composition of the form R1.75(OH)3.75(H2O)1.14, with (OH + H2O)/R = 2·80, which approaches the ratio for a dioctahedral sheet structure.A comparison of these defect chlorites with available data on schuchardtites shows many similarities; however, schuchardtite is not yet sufficiently well denned for the Jacupiranga chlorites to be given this name.

scholarly journals Microstrain Measurement in Plastically Deformed Austenitic Steel

1999 ◽  
Vol 33 (1-4) ◽  
pp. 219-230 ◽  
Author(s):  
K. Hirschi ◽  
M. Ceretti ◽  
P. Lukás ◽  
N. Ji ◽  
C. Braham ◽  
...  
Keyword(s):  
Austenitic Steel ◽  
Metallic Materials ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
X Ray ◽  
Compressive Stresses ◽  
Cold Rolled ◽  
The Mean ◽  
Good Agreement

Some results of high-resolution neutron diffraction experiments resulting in determination of the microstrain in metallic materials are reported. The method of the diffraction line broadening analysis was verified in two materials, investigated earlier by X-ray diffraction: an austenitic steel prestrained up to 30% and a cold rolled aluminium magnesium alloy. For these materials, the mean-square microstrain and the dislocation density were determined, a good agreement was reached with the results of X-ray experiments. As an application of such analysis we investigated the influence of the shot-peening treatment on an austenitic steel. This treatment is commonly used to introduce compressive stresses in the surface of material, giving improved resistance to fatigue fracture. The microstrain distribution and the size of coherently diffracting blocks for a shot-peened sample of austenitic steel as a function of depth from the surface are determined by the above analysis and the results are presented.

The Molecular Structure and Hydrogen Bond Geometry in Liquid Formamide: Electron, Neutron, and X-Ray Diffraction Studies

1983 ◽  
Vol 38 (2) ◽  
pp. 231-236 ◽  
Author(s):  
E. Kálmán ◽  
I. Serke ◽  
G. Pálinkás ◽  
M. D. Zeidler ◽  
F. J. Wiesmann ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Hydrogen Bond ◽  
Electron Diffraction ◽  
Diffraction Data ◽  
Free Molecule ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Mean ◽  
Diffraction Patterns ◽  
Good Agreement

Abstract Electron, neutron and X-ray diffraction patterns of liquid formamide have been measured at a temperature of 25 °C. Analysis of the diffraction data yields the molecular structure and the average geometry of the hydrogen bond. The molecular parameters obtained from liquid diffraction experiments are in good agreement with those from gas electron diffraction for the free molecule. The mean O…N and O…H hydrogen bond distances are 2.9 Å and 1.9 Å, respectively. Four H-bonds per molecule are found on the average. The deviation of the H-bonds from the linearity is estimated.

scholarly journals Crystal structure and computational study of 2,4-dichloro-N-[(E)-(5-nitrothiophen-2-yl)methylidene]aniline

2016 ◽  
Vol 72 (8) ◽  
pp. 1187-1189 ◽  
Author(s):  
Yavuz Köysal ◽  
Hakan Bülbül ◽  
Sümeyye Gümüş ◽  
Erbil Ağar ◽  
Mustafa Serkan Soylu
Keyword(s):  
Crystal Structure ◽  
Computational Study ◽  
Three Dimensional ◽  
Maximum Deviation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Compound C ◽  
Benzene Rings ◽  
The Mean ◽  
Good Agreement

The title compound, C11H6Cl2N2O2S, is a Schiff base that incorporates an N-bound 2,4-dichlorophenyl and a C-bound 5-nitrothiophene ring. The molecule is approximately planar, the maximum deviation from the mean plane being 0.233 (4) Å for the C=N N atom. The dihedral angle between the benzene and thiophene rings is 9.7 (2)°. The C=N double bond has anEconfiguration. The crystal structure features C—H...O hydrogen bonds,forming sheets parallel to (10-1), and π–π stacking interactions between symmetry-related thiophene and benzene rings, in which the distance between adjacent ring centroids is 3.707 (4) Å, forming a three-dimensional supramolecular structure. Geometric parameters from quantum-chemical calculations are in good agreement with experimental X-ray diffraction results.

Isomorphous replacement in electron diffraction of wet crystals of rat hemoglobin

1983 ◽  
Vol 41 ◽  
pp. 446-447
Author(s):  
William F. Tivol ◽  
Murray Vernon King ◽  
D. F. Parsons
Keyword(s):  
Electron Diffraction ◽  
Heavy Atom ◽  
Isomorphous Substitution ◽  
X Ray Diffraction ◽  
Salt Solutions ◽  
X Ray ◽  
Isomorphous Replacement ◽  
Structure Factors ◽  
Diffraction Structure ◽  
The Mean

Feasibility of isomorphous substitution in electron diffraction is supported by a calculation of the mean alteration of the electron-diffraction structure factors for hemoglobin crystals caused by substituting two mercury atoms per molecule, following Green, Ingram & Perutz, but with allowance for the proportionality of f to Z3/4 for electron diffraction. This yields a mean net change in F of 12.5%, as contrasted with 22.8% for x-ray diffraction.Use of the hydration chamber in electron diffraction opens prospects for examining many proteins that yield only very thin crystals not suitable for x-ray diffraction. Examination in the wet state avoids treatments that could cause translocation of the heavy-atom labels or distortion of the crystal. Combined with low-fluence techniques, it enables study of the protein in a state as close to native as possible.We have undertaken a study of crystals of rat hemoglobin by electron diffraction in the wet state. Rat hemoglobin offers a certain advantage for hydration-chamber work over other hemoglobins in that it can be crystallized from distilled water instead of salt solutions.

scholarly journals New Insights into the Crystal Chemistry of Elpidite, Na2Zr[Si6O15]·3H2O and (Na1+YCax□1−X−Y)Σ=2Zr[Si6O15]·(3−X)H2O, and Ab Initio Modeling of IR Spectra

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2160
Author(s):  
Alexander Bogdanov ◽  
Ekaterina Kaneva ◽  
Roman Shendrik
Keyword(s):  
Ir Spectra ◽  
Structural Models ◽  
Chemical Characterization ◽  
Chemical Compositions ◽  
X Ray Diffraction ◽  
Special Group ◽  
X Ray ◽  
Influence Of Water ◽  
Radioactive Species

Elpidite belongs to a special group of microporous zirconosilicates, which are of great interest due to their capability to uptake various molecules and ions, e.g., some radioactive species, in their structural voids. The results of a combined electron probe microanalysis and single-crystal X-ray diffraction study of the crystals of elpidite from Burpala (Russia) and Khan-Bogdo (Mongolia) deposits are reported. Some differences in the chemical compositions are observed and substitution at several structural positions within the structure of the compounds are noted. Based on the obtained results, a detailed crystal–chemical characterization of the elpidites under study was carried out. Three different structure models of elpidite were simulated: Na2ZrSi6O15·3H2O (related to the structure of Russian elpidite), partly Ca-replaced Na1.5Ca0.25ZrSi6O15·2.75H2O (close to elpidite from Mongolia), and a hypothetical CaZrSi6O15·2H2O. The vibration spectra of the models were obtained and compared with the experimental one, taken from the literature. The strong influence of water molecule vibrations on the shape of IR spectra of studied structural models of elpidite is discussed in the paper.

scholarly journals Preparation of high-entropy carbides by different sintering techniques

2021 ◽  
Vol 56 (19) ◽  
pp. 11237-11247 ◽  
Author(s):  
Johannes Pötschke ◽  
Manisha Dahal ◽  
Mathias Herrmann ◽  
Anne Vornberger ◽  
Björn Matthey ◽  
...  
Keyword(s):  
Grain Size ◽  
Single Phase ◽  
X Ray Diffraction ◽  
Vacuum Sintering ◽  
X Ray ◽  
High Entropy ◽  
Mean Grain Size ◽  
The Mean ◽  
Gas Pressure Sintering ◽  
Hardness Values

AbstractDense (Hf, Ta, Nb, Ti, V)C- and (Ta, Nb, Ti, V, W)C-based high-entropy carbides (HEC) were produced by three different sintering techniques: gas pressure sintering/sinter–HIP at 1900 °C and 100 bar Ar, vacuum sintering at 2250 °C and 0.001 bar as well as SPS/FAST at 2000 °C and 60 MPa pressure. The relative density varied from 97.9 to 100%, with SPS producing 100% dense samples with both compositions. Grain size measurements showed that the substitution of Hf with W leads to an increase in the mean grain size of 5–10 times the size of the (Hf, Ta, Nb, Ti, V,)C samples. Vacuum-sintered samples showed uniform grain size distribution regardless of composition. EDS mapping revealed the formation of a solid solution with no intermetallic phases or element clustering. X-ray diffraction analysis showed the structure of mostly single-phase cubic high-entropy carbides. Hardness measurements revealed that (Hf, Ta, Nb, Ti, V)C samples possess higher hardness values than (Ta, Nb, Ti, V, W)C samples.

A DFT study of spherands containing five anisyl groups — Highly preorganized to bind the alkali metal

2006 ◽  
Vol 84 (8) ◽  
pp. 1045-1049 ◽  
Author(s):  
Shabaan AK Elroby ◽  
Kyu Hwan Lee ◽  
Seung Joo Cho ◽  
Alan Hinchliffe
Keyword(s):  
Density Functional Theory ◽  
Binding Energy ◽  
Density Functional ◽  
Ionic Radius ◽  
Binding Energies ◽  
Cavity Size ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray ◽  
Good Agreement

Although anisyl units are basically poor ligands for metal ions, the rigid placements of their oxygens during synthesis rather than during complexation are undoubtedly responsible for the enhanced binding and selectivity of the spherand. We used standard B3LYP/6-31G** (5d) density functional theory (DFT) to investigate the complexation between spherands containing five anisyl groups, with CH2–O–CH2 (2) and CH2–S–CH2 (3) units in an 18-membered macrocyclic ring, and the cationic guests (Li+, Na+, and K+). Our geometric structure results for spherands 1, 2, and 3 are in good agreement with the previously reported X-ray diffraction data. The absolute values of the binding energy of all the spherands are inversely proportional to the ionic radius of the guests. The results, taken as a whole, show that replacement of one anisyl group by CH2–O–CH2 (2) and CH2–S–CH2 (3) makes the cavity bigger and less preorganized. In addition, both the binding and specificity decrease for small ions. The spherands 2 and 3 appear beautifully preorganized to bind all guests, so it is not surprising that their binding energies are close to the parent spherand 1. Interestingly, there is a clear linear relation between the radius of the cavity and the binding energy (R2 = 0.999).Key words: spherands, preorganization, density functional theory, binding energy, cavity size.

Dalnegroite, Tl5–xPb2x(As,Sb)2l–xS34, a new thallium sulphosalt from Lengenbach quarry, Binntal, Switzerland

2009 ◽  
Vol 73 (6) ◽  
pp. 1027-1032 ◽  
Author(s):  
F. Nestola ◽  
A. Guastoni ◽  
L. Bindi ◽  
L. Secco
Keyword(s):  
Polarized Light ◽  
New Mineral ◽  
X Ray Diffraction ◽  
X Ray ◽  
Elemental Concentrations ◽  
Reflected Light ◽  
Mohs Hardness ◽  
The Mean ◽  
The University ◽  
Probable Space

AbstractDalnegroite, ideally Tl4Pb2(As12Sb8)Σ20S34, is a new mineral from Lengenbach, Binntal, Switzerland. It occurs as anhedral to subhedral grains up to 200 μm across, closely associated with realgar, pyrite, Sb-rich seligmanite in a gangue of dolomite. Dalnegroite is opaque with a submetallic lustre and shows a brownish-red streak. It is brittle; the Vickers hardness (VHN25) is 87 kg mm-2(range: 69—101) (Mohs hardness ∼3—3½). In reflected light, dalnegroite is highly bireflectant and weakly pleochroic, from white to a slightly greenish-grey. In cross-polarized light, it is highly anisotropic with bluish to green rotation tints and red internal reflections.According to chemical and X-ray diffraction data, dalnegroite appears to be isotypic with chabournéite, Tl5-xPb2x(Sb,As)21-xS34. It is triclinic, probable space groupP1, witha= 16.217(7) Å,b= 42.544(9) Å,c= 8.557(4) Å, α = 95.72(4)°, β = 90.25(4)°, γ = 96.78(4)°,V= 5832(4) Å3,Z= 4.The nine strongest powder-diffraction lines [d(Å) (I/I0) (hkl)] are: 3.927 (100) (10 0); 3.775 (45) (22); 3.685 (45) (60); 3.620 (50) (440); 3.124 (50) (2); 2.929 (60) (42); 2.850 (70) (42); 2.579 (45) (02); 2.097 (60) (024). The mean of 11 electron microprobe analyses gave elemental concentrations as follows: Pb 10.09(1) wt.%, Tl 20.36(1), Sb 23.95(1), As 21.33(8), S 26.16(8), totalling 101.95 wt.%, corresponding to Tl4.15Pb2.03(As11.86Sb8.20)S34. The new mineral is named for Alberto Dal Negro, Professor in Mineralogy and Crystallography at the University of Padova since 1976.

Local atomic structure in tetragonal pure ZrO2nanopowders

2010 ◽  
Vol 43 (2) ◽  
pp. 227-236 ◽  
Author(s):  
Leandro M. Acuña ◽  
Diego G. Lamas ◽  
Rodolfo O. Fuentes ◽  
Ismael O. Fábregas ◽  
Márcia C. A. Fantini ◽  
...  
Keyword(s):  
Tetragonal Phase ◽  
Local Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atomic Structures ◽  
Crystallite Sizes ◽  
Exafs Study ◽  
The Difference ◽  
X Ray Absorption ◽  
Good Agreement

The local atomic structures around the Zr atom of pure (undoped) ZrO2nanopowders with different average crystallite sizes, ranging from 7 to 40 nm, have been investigated. The nanopowders were synthesized by different wet-chemical routes, but all exhibit the high-temperature tetragonal phase stabilized at room temperature, as established by synchrotron radiation X-ray diffraction. The extended X-ray absorption fine structure (EXAFS) technique was applied to analyze the local structure around the Zr atoms. Several authors have studied this system using the EXAFS technique without obtaining a good agreement between crystallographic and EXAFS data. In this work, it is shown that the local structure of ZrO2nanopowders can be described by a model consisting of two oxygen subshells (4 + 4 atoms) with different Zr—O distances, in agreement with those independently determined by X-ray diffraction. However, the EXAFS study shows that the second oxygen subshell exhibits a Debye–Waller (DW) parameter much higher than that of the first oxygen subshell, a result that cannot be explained by the crystallographic model accepted for the tetragonal phase of zirconia-based materials. However, as proposed by other authors, the difference in the DW parameters between the two oxygen subshells around the Zr atoms can be explained by the existence of oxygen displacements perpendicular to thezdirection; these mainly affect the second oxygen subshell because of the directional character of the EXAFS DW parameter, in contradiction to the crystallographic value. It is also established that this model is similar to another model having three oxygen subshells, with a 4 + 2 + 2 distribution of atoms, with only one DW parameter for all oxygen subshells. Both models are in good agreement with the crystal structure determined by X-ray diffraction experiments.

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