scholarly journals The microstructure of the rapidly solidified foil of the hypoeutectic alloy Sn – 4.4 wt. % Zn

2021 ◽  
pp. 44-52
Author(s):  
Vasili G. Shepelevich ◽  
Denis A. Zernitsa
Keyword(s):  
Diffusion Processes ◽  
Unit Cell ◽  
Hypoeutectic Alloy ◽  
Surface Layers ◽  
Two Phase ◽  
Unequal Distribution ◽  
Cell Parameters ◽  
Zinc Doping ◽  
The Difference ◽  
Rapidly Solidified

The article presents the results of a study of the microstructure of the rapidly solidified foil of the hypoeutectic alloy Sn – 4.4 wt. % Zn. It was found that the investigated alloy has a two-phase structure, which consists of solid solutions of tin and zinc. Doping of tin with zinc leads to a decrease in the unit cell parameter. The difference between the unit cell parameters of a rapidly solidified alloy in comparison with an alloy of pure tin tends to decrease during holding, which is due to strong supercooling of the melt during its production at ultrahigh speeds, and the formation of a supersaturated solid solution of zinc in tin, which, due to high homological temperatures, as a consequence, active diffusion processes, decomposes at room temperature. It has been established that a microcrystalline structure is formed in the foil of the alloy under study, in the cross section of which there are uniformly distributed equiaxed dispersed dark zinc precipitates against the background of a light tin matrix; the absence of zinc plates in the foil reduces the ability to brittle fracture. The unequal distribution of the average chord of random secants on the grains in the surface layers A is caused by the release of heat, which leads to a decrease in the supercooling of the subsequent layers of the melt, and an increase in the grain size as the crystallisation front moves. It was found that in the (301) plane along the [103] direction, tin twinning is observed, which occurs under the action of quenching stresses at high crystallisation rates. The alloy under study has a (100) tin texture, the formation of which is associated with the fact that the (100) plane is the most densely packed, which promotes the growth of grains with this orientation at the highest rate.

Kinematical and Dynamical CBED Pattern Models: Increasing the Accuracy of the Unit-Cell Parameter Measurements Based on CBED Patterns

1990 ◽  
Vol 48 (2) ◽  
pp. 540-541
Author(s):  
I.N. Yadhikov ◽  
S.K. Maksimov
Keyword(s):  
Reciprocal Lattice ◽  
Unit Cell ◽  
Reciprocal Lattice Vector ◽  
Unit Cell Parameters ◽  
Lattice Vector ◽  
Cell Parameters ◽  
Accuracy Of Measurements ◽  
The Difference ◽  
Image Position ◽  
Convergent Beam

Convergent beam electron diffraction (CBED) is widely used as a microanalysis tool. By the relative position of HOLZ-lines (Higher Order Laue Zone) in CBED-patterns one can determine the unit cell parameters with a high accuracy up to 0.1%. For this purpose, maps of HOLZ-lines are simulated with the help of a computer so that the best matching of maps with experimental CBED-pattern should be reached. In maps, HOLZ-lines are approximated, as a rule, by straight lines. The actual HOLZ-lines, however, are different from the straights. If we decrease accelerating voltage, the difference is increased and, thus, the accuracy of the unit cell parameters determination by the method becomes lower.To improve the accuracy of measurements it is necessary to give up the HOLZ-lines substitution by the straights. According to the kinematical theory a HOLZ-line is merely a fragment of ellipse arc described by the parametric equationwith arc corresponding to change of β parameter from -90° to +90°, wherevector, h - the distance between Laue zones, g - the value of the reciprocal lattice vector, g‖ - the value of the reciprocal lattice vector projection on zero Laue zone.

scholarly journals On the Effect of Unit-Cell Parameters in Predicting the Elastic Response of Wood-Plastic Composites

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Fatemeh Alavi ◽  
Amir Hossein Behravesh ◽  
Abbas S. Milani ◽  
Davoud Karimi
Keyword(s):  
Finite Element ◽  
Modulus Of Elasticity ◽  
Strain Curve ◽  
Unit Cell ◽  
Elastic Response ◽  
Geometrical Parameters ◽  
Uniaxial Test ◽  
Cell Parameters ◽  
Plastic Composite ◽  
The Difference

This paper presents a study on the effect of unit-cell geometrical parameters in predicting elastic properties of a typical wood plastic composite (WPC). The ultimate goal was obtaining the optimal values of representative volume element (RVE) parameters to accurately predict the mechanical behavior of the WPC. For each unit cell, defined by a given combination of the above geometrical parameters, finite element simulation in ABAQUS was carried out, and the corresponding stress-strain curve was obtained. A uniaxial test according to ASTM D638-02a type V was performed on the composite specimen. Modulus of elasticity was determined using hyperbolic tangent function, and the results were compared to the sets of finite element analyses. Main effects of RVE parameters and their interactions were demonstrated and discussed, specially regarding the inclusion of two adjacent wood particles within one unit cell of the material. Regression analysis was performed to mathematically model the RVE parameter effects and their interactions over the modulus of elasticity response. The model was finally employed in an optimization analysis to arrive at an optimal set of RVE parameters that minimizes the difference between the predicted and experimental moduli of elasticity.

The f.c.c.+tetragonal two-phase region of the Cu–Ni–Zn system

1983 ◽  
Vol 16 (1) ◽  
pp. 99-102 ◽  
Author(s):  
O. S. Mayall
Keyword(s):  
Tetragonal Phase ◽  
Lattice Spacing ◽  
Single Phase ◽  
Phase Region ◽  
Unit Cell ◽  
Unit Cell Parameters ◽  
Two Phase ◽  
Cell Parameters ◽  
Tie Lines

The f.c.c. + tetragonal two-phase region of the Cu–Ni–Zn system has been delineated, and unit-cell parameters along the boundaries determined. Apparently anomalous parameter measurements prevented the determination of the tie lines. A pattern of diffraction broadening from the tetragonal phase common to both the two-phase and single-phase regions was related to the variation in lattice spacing of the tetragonal phase along the boundary. Reasons for this broadening are discussed.

Packing analysis of carbohydrates and polysaccharides. 16. The crystal structures of celluloses IVI and IVII

1985 ◽  
Vol 63 (1) ◽  
pp. 173-180 ◽  
Author(s):  
Eric S. Gardiner ◽  
Anatole Sarko
Keyword(s):  
Crystal Structures ◽  
Unit Cell ◽  
Hydroxyl Groups ◽  
Data Sets ◽  
Cell Parameters ◽  
The Difference ◽  
Cellulose Iv ◽  
Chain Conformations ◽  
Probable Space ◽  
Packing Analysis

The crystal structures of cellulose polymorphs IVI and IVII have been determined by X-ray fiber diffraction analysis combined with stereochemical model refinement. Both structures crystallize in a two-chain unit cell of essentially identical parameters. The most probable space group in both cases is P1. The chain conformations, although close to two-fold helical, are marked by unequal rotational positions of the O(6) hydroxyl groups in adjacent residues. Despite identical unit cell parameters, the structures differ in chain polarity: in cellulose IVI both chains of the unit cell are parallel, whereas in cellulose IVII they are antiparallel. The difference in polarity is further substantiated by the results of chemical conversions which show that cellulose IVI is converted to cellulose I, and cellulose IVII is converted to cellulose II, via parallel and antiparallel cellulose triacetates, respectively. The reliability of the structure analyses is indicated by the residual R″ = 0.115 for cellulose IVI and 0.094 for cellulose IVII, for data sets of 41 and 43 reflections, respectively.

Isomorphism and mixed crystals in 2-R-naphthalenes: evidence of structural subfamilies and prediction of metastable forms

1999 ◽  
Vol 32 (3) ◽  
pp. 481-488 ◽  
Author(s):  
Y. Haget ◽  
N. B. Chanh ◽  
A. Meresse ◽  
L. Bonpunt ◽  
F. Michaud ◽  
...  
Keyword(s):  
High Temperature ◽  
Unit Cell ◽  
Mixed Crystals ◽  
Unit Cell Parameters ◽  
Two Phase ◽  
Cell Parameters ◽  
Solid Liquid ◽  
Metastable Forms

Solid–liquid binary phase diagrams and isothermal unit-cell parameters as a function of composition are given for the high-temperature form (P21/a,Z= 2) mixed crystals generated by 2-fluoronaphthalene, naphthalene and 2-naphthol with four other β derivatives of naphthalene. The study leads to the distinction between two high-temperature forms (or types of packing). The first one (type 1) is taken by five 2-R-naphthalenes (R= F, Cl, Br, SH, CH3; the first subfamily), the second one (type 2) by naphthalene itself and 2-naphthol (R= H, OH; the second subfamily). The crystallographic data also allow an estimation of unit-cell parameters for the metastable forms of naphthalene (type 1,a= 8.0,b= 5.95,c= 8.6 Å, β = 116°) and 2-fluoronaphthalene (type 2,a= 8.336,b= 5.915,c= 9.000 Å, β = 122.23°), supporting an interpretation, in terms of crossed isodimorphism, of the observed two-phase regions in systems in which the components do not belong to the same subfamily.

X-ray diffraction study on YBa2Cu3O7−δ with BaCuO2 addition

2010 ◽  
Vol 25 (S1) ◽  
pp. S52-S54
Author(s):  
Sheng Xu ◽  
Xiaoshan Wu ◽  
Yanni Gu
Keyword(s):  
Unit Cell ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Solid Reaction ◽  
Two Phase ◽  
Powder Mixtures ◽  
Rietveld Refinements ◽  
X Ray ◽  
Cell Parameters ◽  
Polycrystalline Powder

Two-phase polycrystalline powder mixtures of YBa2Cu3O7−δ (YBCO) and xBaCuO2 (x=0, 0.05, 0.1, 0.2, and 0.3) were prepared by solid reaction. The Rietveld refinements of X-ray powder diffraction data show that BaCuO2 addition was successfully produced in superconductor YBCO and the unit-cell parameters of YBCO reach a maximum at x=0.05. The critical current density (Jc) also reaches a maximum at x=0.05 and then decreases sharply with increasing amount of BaCuO2. The change of Jc as a function of x was found to be similar to those of the unit-cell parameters. The characteristic behavior of Jc may come from the structure-parameter change of YBCO caused by BaCuO2 addition.

scholarly journals Heat capacity and thermal expansion of yttrium tantalate

2019 ◽  
Vol 484 (2) ◽  
pp. 181-183
Author(s):  
A. V. Khoroshilov ◽  
A. A. Ashmarin ◽  
V. N. Guskov ◽  
E. G. Sazonov ◽  
K. S. Gavrichev ◽  
...  
Keyword(s):  
Differential Scanning Calorimetry ◽  
Heat Capacity ◽  
Thermal Expansion ◽  
Heat Capacities ◽  
Unit Cell ◽  
Unit Cell Parameters ◽  
Scanning Calorimetry ◽  
Crystal Lattices ◽  
Cell Parameters ◽  
The Difference

The isobaric heat capacities of two monoclinic (M' and M) modifications of yttrium orthotantalate at temperatures 5–1300 K have been measured by the adiabatic and differential scanning calorimetry methods. It has been demonstrated that the difference in structure between the crystal lattices of M' and M has small effect in the heat capacity, and the difference between the heat capacities of these phases Cp(M)-Cp(M') is small, always positive, and increases in the range of the lowest temperatures. The unit cell parameters of M-YTaO4 have been determined as a function of temperature in the range 300–1173 K.

X-ray powder diffraction analysis of a new magnesium chromate hydrate, MgCrO4·11H2O

2012 ◽  
Vol 27 (1) ◽  
pp. 8-11 ◽  
Author(s):  
A. Dominic Fortes ◽  
Ian G. Wood
Keyword(s):  
Hydrogen Bond ◽  
Diffraction Analysis ◽  
Powder Diffraction ◽  
Unit Cell ◽  
Hydrogen Bond Network ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Bond Network ◽  
The Difference

A new hydrate of magnesium chromate is synthesized by quenching aqueous solutions of MgCrO4 in liquid nitrogen. MgCrO4·11H2O is isostructural with the rare mineral meridianiite (MgSO4·11H2O) being triclinic, $P{\bar 1}$, Z = 2, with unit-cell parameters a = 6.811 33(8) Å, b = 6.958 39(9) Å, c = 17.3850(2) Å, α = 87.920(1)°, β = 89.480(1)°, γ = 62.772(1)°, and V = 732.17(1) Å3 at −15 °C. The difference in unit-cell parameters between SO4- and CrO4-bearing species is only partially accounted for by the difference in S–O and Cr–O bond lengths; the remainder of the difference (over 90% in the cell volume) is attributed to weakening of the interpolyhedral hydrogen-bond network.

Shock consolidation of Ni-Ti alloy powder

1986 ◽  
Vol 44 ◽  
pp. 430-431
Author(s):  
Naresh N. Thadhani ◽  
Thad Vreeland ◽  
Thomas J. Ahrens
Keyword(s):  
Alloy Powder ◽  
Amorphous Material ◽  
Ti Alloy ◽  
Two Phase ◽  
Near Surface ◽  
Optical Micrograph ◽  
Shock Compaction ◽  
Powder Particles ◽  
Ti Powder ◽  
Rapidly Solidified

A spherically-shaped, microcrystalline Ni-Ti alloy powder having fairly nonhomogeneous particle size distribution and chemical composition was consolidated with shock input energy of 316 kJ/kg. In the process of consolidation, shock energy is preferentially input at particle surfaces, resulting in melting of near-surface material and interparticle welding. The Ni-Ti powder particles were 2-60 μm in diameter (Fig. 1). About 30-40% of the powder particles were Ni-65wt% and balance were Ni-45wt%Ti (estimated by EMPA).Upon shock compaction, the two phase Ni-Ti powder particles were bonded together by the interparticle melt which rapidly solidified, usually to amorphous material. Fig. 2 is an optical micrograph (in plane of shock) of the consolidated Ni-Ti alloy powder, showing the particles with different etching contrast.

Sectioned rubisco crystals in TEM

1990 ◽  
Vol 48 (3) ◽  
pp. 664-665
Author(s):  
Gunnel Karlsson ◽  
Jan-Olov Bovin ◽  
Michael Bosma
Keyword(s):  
Plant Cell ◽  
Carbon Fixation ◽  
Unit Cell ◽  
Protein Crystals ◽  
Unit Cell Parameters ◽  
Cell Parameters ◽  
Photosynthetic Carbon Fixation ◽  
Photosynthetic Carbon

RuBisCO (D-ribulose-l,5-biphosphate carboxylase/oxygenase) is the most aboundant enzyme in the plant cell and it catalyses the key carboxylation reaction of photosynthetic carbon fixation, but also the competing oxygenase reaction of photorespiation. In vitro crystallized RuBisCO has been studied earlier but this investigation concerns in vivo existance of RuBisCO crystals in anthers and leaves ofsugarbeets. For the identification of in vivo protein crystals it is important to be able to determinethe unit cell of cytochemically identified crystals in the same image. In order to obtain the best combination of optimal contrast and resolution we have studied different staining and electron accelerating voltages. It is known that embedding and sectioning can cause deformation and obscure the unit cell parameters.

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