Study of the Phases of Mg-Zn-La Magnesium Alloys at 150°C

2013 ◽  
Vol 750-752 ◽  
pp. 679-682 ◽  
Author(s):  
Ming Li Huang ◽  
Li Na Dong ◽  
Ying Ling Wang ◽  
Li Wei Quan
Keyword(s):  
Phase Equilibrium ◽  
Lattice Structure ◽  
Stable Phase ◽  
X Ray Diffraction ◽  
Binary Solid Solution ◽  
Two Phase ◽  
X Ray ◽  
The Difference ◽  
The Stability ◽  
T Phase

Alloys with different compositions in Mg-rich corner of Mg-Zn-La system at 150°C were prepared, and the phase equilibrium in Mg-Zn-La alloys were determined by scanning electron microscopy (SEM), electron probe microanalysis based on energy dispersive X-ray spectroscopy (EPMA-EDS) and X-ray diffraction (XRD). The stability, compositions and lattice structures of the intermetallic compounds of Mg-Zn-La alloys were identified. The results show that, there exists a ternary compound (T-phase) with constant La (about 8at%) and the changed ratio of Mg/Zn in the Mg-rich corner of Mg-Zn-La system. Though the ratio of (Mg, Zn)/La of T-phase is close to that of Mg/La of Mg12La, the T-phase was not the binary solid solution of Mg12La because of the difference of the lattice structure. It also reveals that T-phase is a stable phase, and it is in two-phase equilibrium of T-phase+Mg at 150°C.

The stability and screw sense of the α -helix in poly- β -benzyl-L-aspartate

1960 ◽  
Vol 259 (1296) ◽  
pp. 110-128 ◽  
Keyword(s):  
Optical Rotatory Dispersion ◽  
Molecular Models ◽  
X Ray Diffraction ◽  
X Ray ◽  
Left Handed ◽  
The Difference ◽  
Diffraction Patterns ◽  
The Stability ◽  
Α Helix ◽  
The Right

A number of polymers and copolymers containing β -benzyl-L-aspartate has been prepared and their optical rotatory dispersion in a variety of solvents has been measured. The results of these measurements together with studies of infra-red spectra, X-ray diffraction patterns, deuteration rates and molecular models lead to the following conclusions. (i) The α -helical form of poly- β -benzyl-L-aspartate is considerably less stable relative to the solvated randomly coiled form than that of poly- γ -benzyl-L-glutamate. (ii) The left-handed α -helix of poly- β -benzyl-L-aspartate is more stable than the right-handed one. (iii) The difference in stability between the two senses of α -helix is much less in the case of poly- β -benzyl-L-aspartate than in that of poly- γ -benzyl-L-glutamate or poly-L-alanine.

The stability of the lattice structure in low salt T-state haemoglobin crystals

1993 ◽  
Vol 442 (1914) ◽  
pp. 193-205 ◽  
Keyword(s):  
Lattice Structure ◽  
Special Property ◽  
Structural Basis ◽  
Salt Bridges ◽  
X Ray Diffraction ◽  
Salt Solutions ◽  
X Ray ◽  
Low Salt ◽  
The Stability ◽  
T State

The reconstruction of the electron density of molecules in crystals from X-ray diffraction measurements depends on the exactness of the packing of the molecules in the unit cell and the crystal lattice. Crystals of T-state haemoglobin, the low affinity form of the molecule, grow from high salt solutions or from low salt solutions in the presence of polyethylene glycol. The low salt lattice has the special property that it allows the haemoglobin molecule to bind oxygen and other ligands without the crystal breaking up. The stability of the low salt T-state crystals appears to arise from a small number of well-defined salt bridges and hydrogen bonds that are concentrated in specific lattice directions. These together form a framework within which the molecule can make adjustments which are sufficient to accommodate ligand binding but in which the larger quaternary movements normally associated with oxygenation are prevented. In these crystals therefore interactions with ligands can be studied directly by X-ray diffraction and the structural basis of the T-state’s low affinity for oxygen can be analysed.

scholarly journals Theoretical Investigations of a BN Polymorph with sp2 + sp3 Hybridizations

Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1574
Author(s):  
Xinhai Yu ◽  
Riguge Su ◽  
Bei He ◽  
Binchang Ma
Keyword(s):  
Density Functional ◽  
Mechanical Anisotropy ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray ◽  
Theoretical Investigations ◽  
M Phase ◽  
The Difference ◽  
The Stability ◽  
Xrd Patterns

The crystal structure, mechanical anisotropy, elastic properties and electronic characteristics, as well as the stability, of P4/m BN are predicted by means of density functional theory. In this work, BN in the P4/m phase demonstrates mechanical and dynamical stability. Compared with the values of bulk B, E and G in the P4/m phase, the B of BN in the P4/m phase is greater than that of dz4 BN, while the G and E of P4/m BN are greater than those of Pnc2 BN and dz4 BN. The ratio of the bulk-to-shear modulus for P4/m BN is less than 1.75 and dz4 BN, dz2 BN and lzlz2 BN, indicating that P4/m BN is more brittle than dz4 BN, dz2 BN and lzlz2 BN. P4/m BN exhibits stronger mechanical anisotropy in G and E than Pbca BN, P42/mnm BN and Pm-3m BN but much weaker mechanical anisotropy than P4/mbm BN, B7N7, B11N11 and B15N15. In addition, P4/m BN is a quasi-direct bandgap semiconductor, and the difference between the direct and the indirect bandgap is 0.008 eV. In order to obtain further characteristics of P4/m BN for future synthetic verification, the X-ray diffraction (XRD) patterns for P4/m BN are also calculated. Given its properties, P4/m BN is a good candidate for photoelectric devices.

A computer program for the deconvolution of X-ray diffraction profiles with the composite of Pearson type VII functions

1983 ◽  
Vol 16 (6) ◽  
pp. 653-657 ◽  
Author(s):  
H. Toraya ◽  
M. Yoshimura ◽  
S. Sōmiya
Keyword(s):  
Computer Program ◽  
Computation Time ◽  
X Ray Diffraction ◽  
Diffraction Profile ◽  
X Ray ◽  
Pearson Type ◽  
Spurious Oscillations ◽  
Data Function ◽  
The Difference ◽  
The Stability

A computer program for the deconvolution of X-ray diffraction profiles has been written in Fortran IV. The deconvolution procedure is based on the minimization of the difference between the observed data function and a calculated function, where the latter is the convolution of the instrumental function and the true data function approximated with an analytical expression. The composite of two asymmetric Pearson type VII functions was assumed to represent the true data function, and the simplex method was used for the minimization. The stability of convergence and the influences of the truncation effect and the step width of intensity data on the deconvoluted profile were examined. The computer program can deconvolute the X-ray diffraction profile in moderate computation time without generating spurious oscillations due to the truncation effect.

Crystallization and Phase Transformation of ZrO2-SiO2 Gels

1990 ◽  
Vol 180 ◽  
Author(s):  
Xiaoming Li ◽  
P.F. Johnson
Keyword(s):  
Phase Transformation ◽  
Gravimetric Analysis ◽  
Acetate Solution ◽  
X Ray Diffraction ◽  
Transformation Behavior ◽  
X Ray ◽  
Zirconium Acetate ◽  
The Stability ◽  
T Phase ◽  
Initial Crystallization Temperature

ABSTRACTPure SiO2, ZrO2 and SiO2−ZrO2 gels have been prepared by hydrolysis and gelation of tetraethylorthosilicate (TEOS) and zirconium acetate solution. The crystallization and phase transformation of SiO2 and ZrO2 in these gels have been followed up to 1450°C using differential thermal analysis (DTA), thermal gravimetric analysis (TGA) and X-ray diffraction analysis (XRD). The crystallization and phase transformation behavior of SiO2 or ZrO2 is quite different in different gel systems. It was found that in pure SiO2 gel, the cristobalite phase was precipitated out at about 1000°C. In the pure ZrO2 system, tetragonal (t−) phase zirconia was crystallized at about 430°C, t-ZrO2 crystals grew three dimensionally and the activation energy for growth was calculated as about 365 kJmol−1. But in the SiO2-ZrO2 system, the presence of ZrO2 suppressed the crystallization of SiO2 , and SiO2 increased the initial crystallization temperature and the stability of t-ZrO2.

scholarly journals Effect of tempering on thermal analysis of Al-Ti-Si alloy and its composites

2019 ◽  
Vol 14 (31) ◽  
pp. 89-98
Author(s):  
Rana Afif Anaee
Keyword(s):  
Thermal Analysis ◽  
Chemical Composition ◽  
Base Alloy ◽  
S Phase ◽  
Stable Phase ◽  
Dsc Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Sic Particles ◽  
The Stability

The investigation of the effect of tempering on thermal analysis ofAl-Ti-Si alloy and its composites with MgO and SiC particles wasperformed. Thermal analysis was performed before and aftertempering by DSC scan. Optical microscopy was used to identify thephases and precipitations that may be formed in base alloy andcomposites. X-ray diffraction test indicated that the Al3Ti is the mainphase in Al-Ti-Si alloy in addition to form Al5Ti7Si12 phase. Somechemical reactions can be occurred between reinforcements andmatrix such as MgO.Al2O3 in Al-Ti/MgO, and Al4C3 and Al(OH)3 inAl-Ti/SiC composite. X-ray florescence technique is used toinvestigate the chemical composition of the fabricated specimens.Heat treatment (Tempering) changes the microstructure of base alloyand its composites which was assessed by DSC scan. Generally,three main peaks appeared in DSC represented by GP zone, S phase(precipitations) and dissolution of phases or precipitations. Aftertempering, composite with SiC particles showed better results thanbase alloy and composite with MgO. Since the optical microscopyrevealed reforming the stable phase Al3Ti with evaporation somegases from composite. DSC analysis showed the stability ofcomposite with SiC was up to 270oC.

Antiphase Boundaries in Ordered Ni3FE Crystals

1969 ◽  
Vol 27 ◽  
pp. 62-63
Author(s):  
Y. H. Liu
Keyword(s):  
Domain Size ◽  
Antiphase Domain ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hardening Mechanism ◽  
Superlattice Structure ◽  
Disordered Phase ◽  
Domain Boundaries ◽  
Atomic Scattering ◽  
The Difference

Ordered Ni3Fe crystals possess a LI2 type superlattice similar to the Cu3Au structure. The difference in slip behavior of the superlattice as compared with that of a disordered phase has been well established. Cottrell first postulated that the increase in resistance for slip in the superlattice structure is attributed to the presence of antiphase domain boundaries. Following Cottrell's domain hardening mechanism, numerous workers have proposed other refined models also involving the presence of domain boundaries. Using the anomalous X-ray diffraction technique, Davies and Stoloff have shown that the hardness of the Ni3Fe superlattice varies with the domain size. So far, no direct observation of antiphase domain boundaries in Ni3Fe has been reported. Because the atomic scattering factors of the elements in NijFe are so close, the superlattice reflections are not easily detected. Furthermore, the domain configurations in NioFe are thought to be independent of the crystallographic orientations.

Fractionation of polymethylene chains: An electron crystallographic investigation

1986 ◽  
Vol 44 ◽  
pp. 794-795
Author(s):  
Douglas L. Dorset
Keyword(s):  
Cross Section ◽  
Binary Systems ◽  
Linear Chain ◽  
Pure Component ◽  
Organic Substrates ◽  
Crystallographic Investigation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Molecular Sizes ◽  
The Stability

A variety of linear chain materials exist as polydisperse systems which are difficultly purified. The stability of continuous binary solid solutions assume that the Gibbs free energy of the solution is lower than that of either crystal component, a condition which includes such factors as relative molecular sizes and shapes and perhaps the symmetry of the pure component crystal structures.Although extensive studies of n-alkane miscibility have been carried out via powder X-ray diffraction of bulk samples we have begun to examine binary systems as single crystals, taking advantage of the well-known enhanced scattering cross section of matter for electrons and also the favorable projection of a paraffin crystal structure posited by epitaxial crystallization of such samples on organic substrates such as benzoic acid.

scholarly journals Stable and Metastable Phase Equilibria Involving the Cu6Sn5 Intermetallic

2021 ◽  
Author(s):  
A. Leineweber ◽  
M. Löffler ◽  
S. Martin
Keyword(s):  
Phase Equilibria ◽  
Electron Backscatter Diffraction ◽  
Metastable Phase ◽  
Stable Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Heat Treated ◽  
Ordered Phases ◽  
Backscatter Diffraction ◽  
Kinetics Of

Abstract Cu6Sn5 intermetallic occurs in the form of differently ordered phases η, η′ and η′′. In solder joints, this intermetallic can undergo changes in composition and the state of order without or while interacting with excess Cu and excess Sn in the system, potentially giving rise to detrimental changes in the mechanical properties of the solder. In order to study such processes in fundamental detail and to get more detailed information about the metastable and stable phase equilibria, model alloys consisting of Cu3Sn + Cu6Sn5 as well as Cu6Sn5 + Sn-rich melt were heat treated. Powder x-ray diffraction and scanning electron microscopy supplemented by electron backscatter diffraction were used to investigate the structural and microstructural changes. It was shown that Sn-poor η can increase its Sn content by Cu3Sn precipitation at grain boundaries or by uptake of Sn from the Sn-rich melt. From the kinetics of the former process at 513 K and the grain size of the η phase, we obtained an interdiffusion coefficient in η of (3 ± 1) × 10−16 m2 s−1. Comparison of this value with literature data implies that this value reflects pure volume (inter)diffusion, while Cu6Sn5 growth at low temperature is typically strongly influenced by grain-boundary diffusion. These investigations also confirm that η′′ forming below a composition-dependent transus temperature gradually enriches in Sn content, confirming that Sn-poor η′′ is metastable against decomposition into Cu3Sn and more Sn-rich η or (at lower temperatures) η′. Graphic Abstract

scholarly journals A Superhydrophobic, Antibacterial, and Durable Surface of Poplar Wood

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1885
Author(s):  
Xinyu Wu ◽  
Feng Yang ◽  
Jian Gan ◽  
Zhangqian Kong ◽  
Yan Wu
Keyword(s):  
Stearic Acid ◽  
Antibacterial Properties ◽  
Alkali Resistance ◽  
Poplar Wood ◽  
X Ray Diffraction ◽  
X Ray ◽  
Different Temperatures ◽  
Acid And Alkali Resistance ◽  
The Stability

The silver particles were grown in situ on the surface of wood by the silver mirror method and modified with stearic acid to acquire a surface with superhydrophobic and antibacterial properties. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray energy spectroscopy (XPS) were used to analyze the reaction mechanism of the modification process. Scanning electron microscopy (SEM) and contact angle tests were used to characterize the wettability and surface morphology. A coating with a micro rough structure was successfully constructed by the modification of stearic acid, which imparted superhydrophobicity and antibacterial activity to poplar wood. The stability tests were performed to discuss the stability of its hydrophobic performance. The results showed that it has good mechanical properties, acid and alkali resistance, and UV stability. The durability tests demonstrated that the coating has the function of water resistance and fouling resistance and can maintain the stability of its hydrophobic properties under different temperatures of heat treatment.

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