Diffusion of Boron in Cobalt Sinters

2013 ◽  
Vol 58 (4) ◽  
pp. 1131-1136 ◽  
Author(s):  
J. Borowiecka-Jamrozek ◽  
J. Lachowski
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Mechanism ◽  
Reaction Diffusion ◽  
Optical Microscope ◽  
Process Time ◽  
Interatomic Potentials ◽  
X Ray Diffraction ◽  
Two Phase ◽  
Calculation Results ◽  
Two Phases

Abstract The paper describes the process of diffusion taking place at the surface of sinters produced from Co Extrafine powder after saturation with boron. Boronizing was performed at a temperature of 950°C for 6 and 12 hours by applying B4C powder as a depositing source, NH4Cl + NaF as an activator and Al2O3 as an inert filler. The study involved determining the diffusion coefficient, which required analyzing the microstructure and thickness of the layers and the process time. The images obtained with a Leica DM-4000 optical microscope revealed a two-phase structure of the boride layers. The presence of the two phases, i.e. CoB and Co2B, was confirmed by X-ray diffraction (XRD). A model of diffusion of boron atoms into the cobalt substrate was developed assuming the reaction diffusion mechanism. This model was used to calculate the diffusion coefficient. It required taking account of the interatomic potentials of boron and cobalt. The calculation results were compared with the experimental data concerning the diffusion of boron in other materials.

Phase Transformation in Granular Alloys of Cu2S-Ni3S2-Na2S System

2014 ◽  
Vol 353 ◽  
pp. 263-268
Author(s):  
Evgeny N. Selivanov ◽  
L.Yu. Udoeva ◽  
N.I. Selmenskich
Keyword(s):  
Solid Solution ◽  
X Ray Diffraction ◽  
Two Phase ◽  
Hydrometallurgical Processing ◽  
Degree Of Separation ◽  
Large Particles ◽  
Dendrite Solidification ◽  
Sulfide Melt ◽  
Two Phases ◽  
Granular Alloys

The effect of Na2S on the phase composition and microstructure of tempered Cu2S-Ni3S2 alloys was studied by X-ray diffraction, optical microscopy and electron probe microanalysis (EPMA). It was found that quick crystallization of the sulfide melt leads to separation into two phases - Ni3S2 and a solid solution of Cu2S with Na2Cu4S5, moreover, nickel is concentrated in large particles and copper – in small ones. In contrast to the fine dendrite solidification of granular Cu2S-Ni3S2 alloys, in the ternary system there is a well-defined two-phase microstructure with rounded borders of the interface. Friability and a low microhardness of Cu2S - Na2Cu4S5 solid solution provide an autodecomposition of the sulfides melt by quenching into water (granulation). The degree of separation of copper and nickel depends on the overheating temperature and a quantity of Na2S in melt. The results can be used to hydrometallurgical processing of copper-nickel convert matt.

Two-Phase Structure of Fluorinated Powdered Silica Resulting from Deep Processing of Rice Wastes

2018 ◽  
Vol 7 (1) ◽  
pp. 38-44 ◽  
Author(s):  
А. Рашковский ◽  
A. Rashkovskiy ◽  
Е. Политова ◽  
E. Politova ◽  
А. Меркушкин ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Inductively Coupled Plasma ◽  
Physicochemical Analysis ◽  
Nano Particles ◽  
Deep Processing ◽  
X Ray Diffraction ◽  
Two Phase ◽  
X Ray ◽  
Inductively Coupled ◽  
Two Phases

In this investigation the structure of «green» silica maid with rice husk has been studied by methods of physicochemical analysis. By method of X-ray diffraction it has been found that the samples of «green» silica powders are completely amorphous, and the observed amorphous halo consists of two components. By method of scanning electron microscopy it has been revealed that nano-particles of «green» SiO2 can form agglomerates and microstructures with dimensions from 0,1 to 500 microns, containing numerous pores, which presence has been confirmed by sorption measurements. By method of mass spectrometry with inductively coupled plasma has been found the presence of aluminum, titanium and nickel mechanical impurities in the «green» SiO2 powders. By method of X-ray photoelectron spectroscopy significant amount of fluorine atoms in «green» silica (up to 5% (at.)) has been revealed, which could be introduced in SiO2 in the process of its preparation. In such a case, it was found that fluorine interacts with «green» silica by means of two mechanisms, leading to appearance of two phases within fluorinated powders of «green» SiO2.

Experimental investigation on thermodynamic properties and crystal structure of La 0.78Ba0.22MnO3 compounds

2020 ◽  
Vol 34 (11) ◽  
pp. 2050101
Author(s):  
R. F. Hashimov ◽  
F. A. Mikailzade ◽  
S. V. Trukhanov ◽  
A. V. Trukhanov ◽  
D. M. Mirzayeva
Keyword(s):  
Crystal Structure ◽  
Diffraction Method ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Thermo Gravimetric ◽  
Two Phase ◽  
Cubic Symmetry ◽  
Space Group ◽  
Two Phases ◽  
Rhombohedral Symmetry

In this work, powder [Formula: see text] samples (purity of 99.99 % and density of [Formula: see text] were used. The crystal structure of [Formula: see text] compound was studied by X-ray diffraction method. It was determined that the crystal structure of this compound consists of two phases at room-temperature and under normal condition. These structure phases correspond to the cubic symmetry with Pm-3m space group and rhombohedral symmetry with the R-3c space group. Thermo Gravimetric (TG), Differential Scanning Calorimetry (DSC), Differential Thermo Gravimetric (DTG) and Differential Thermal Analysis (DTA) of [Formula: see text] compound were carried out in a high-temperature range of [Formula: see text]. It has been found that at high-temperatures, two-phase transition occurs in this compound. The value of thermodynamic parameters was found out for each phase transit.

scholarly journals Crystal structure of morimotoite from Ice River, Canada

2014 ◽  
Vol 29 (4) ◽  
pp. 325-330 ◽  
Author(s):  
Sytle M. Antao
Keyword(s):  
Crystal Structure ◽  
Rietveld Method ◽  
Phase 1 ◽  
Site Occupancy ◽  
X Ray Diffraction ◽  
Alkaline Complex ◽  
Two Phase ◽  
Homogeneous Sample ◽  
Weight Percentage ◽  
Two Phases

The crystal structure of a morimotoite garnet, ideally Ca3(Ti4+Fe2+)Si3O12, from the Ice River alkaline complex, British Columbia, Canada was refined by the Rietveld method, space group $Ia\overline 3 d$, and monochromatic synchrotron high-resolution powder X-ray diffraction (HRPXRD) data. Electron-microprobe analysis indicates a homogeneous sample with a formula {Ca2.91Mg0.05Mn2+0.03}Σ3[Ti1.09Fe3+0.46Fe2+0.37Mg0.08]Σ2(Si2.36Fe3+0.51Al0.14)Σ3O12. The HRPXRD data show a two-phase intergrowth. The reduced χ2 and overall R(F2) Rietveld refinement values are 1.572 and 0.0544, respectively. The weight percentage, unit-cell parameter (Å), distances (Å), and site occupancy factors (sofs) for phase-1 are as follows: 76.5(1)%, a = 12.156 98(1) Å, average <Ca–O> = 2.4383, Ti–O = 2.011(1), Si–O = 1.693(1) Å, Ca(sof) = 0.943(2), Ti(sof) = 0.966(2), and Si(sof) = 1.095(3). The corresponding values for phase-2 are 23.5(1)%, a = 12.160 67(2) Å, average <Ca–O> = 2.452, Ti–O = 1.988(3), Si–O = 1.704(3) Å, Ca(sof) = 1.063(7), Ti(sof) = 1.187(7), and Si(sof) = 1.220(8). The two phases cause strain that arises from structural mismatch and gives rise to low optical anisotropy. Because the two phases are structurally quite similar, a refinement using a single-phase model with anisotropic displacement parameters shows no unusual displacement ellipsoid for the O atom that requires a “split O-atom position”, as was done in previous studies.

Microstructure and Phase Transformation Temperatures of Two-Phase FeAl (B2) + FeAl2 Alloys

2014 ◽  
Vol 1760 ◽  
Author(s):  
Xiaolin Li ◽  
Martin Palm ◽  
Anke Scherf ◽  
Daniel Janda ◽  
Martin Heilmaier ◽  
...  
Keyword(s):  
Composition Dependence ◽  
Composition Range ◽  
Lamellar Microstructure ◽  
Lamellar Spacing ◽  
Al Alloys ◽  
X Ray Diffraction ◽  
Two Phase ◽  
Creep Ductility ◽  
Heat Treated ◽  
Two Phases

ABSTRACTFe-Al alloys with about 55 to 65 at.% Al undergo a eutectoid transformation at 1095 °C: Fe5Al8 (ε) ↔ FeAl + FeAl2. Hence, as-cast Fe-Al alloys in this composition range show a very fine-scaled lamellar microstructure (average lamellar spacing below 500 nm) consisting of the two phases FeAl and FeAl2. The microstructure looks similar to the α2 + γ lamellar microstructure of Ti-Al-based alloys, which is known for having well-balanced properties in terms of creep, ductility and strength. However, there is limited knowledge about the properties of Fe-Al-based alloys in this composition range. In this study, a series of as-cast as well as heat-treated Fe-Al alloys with compositions between 57 and 63 at.% Al were investigated. The microstructures and crystal structures were analysed by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The composition dependence of all transition temperatures was obtained by differential thermal analysis (DTA).

Synthesis and Characterization of Thermoplastic Biomaterial Based on Acylated Chitosan Oligosaccharide

2011 ◽  
Vol 117-119 ◽  
pp. 1433-1436 ◽  
Author(s):  
Feng Hong Li ◽  
Yong Sun ◽  
San Xi Li ◽  
Shao Jun Ma
Keyword(s):  
Optical Microscope ◽  
Chitosan Oligosaccharide ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Two Phase ◽  
X Ray ◽  
Chemical Structures ◽  
Chitosan Oligosaccharides ◽  
Diffraction Peaks

A series of acylated chitosan oligosaccharides (LCSOs) were synthesized by reacting chitosan oligosaccharide (CSO) with lauroyl chloride in methane sulfonic acid. The chemical structures of LCSOs were characterized by Fourier transform infrared. Differential scanning calorimetry (DSC) showed that LCSOs had two phase transitions during heating. Thermoplastic chitosan oligosaccharide (LCSO-4) has distinct melting temperature (Tm) at 64 °C and 110°C. X-ray diffraction (XRD) analyses indicated that the crystal structure of CSO was changed through acylation and had created new crystal domains of lauroyl side chains. New strong diffraction peaks were observed around 2θ values of 20.0°, 21.5° and 26.3° for thermoplastic acylated chitosan oligosaccharide (LCSO-4). The melting and crystallization properties of thermoplastic acylated chitosan oligosaccharide were observed by polarized optical microscope (POM).

Defect structures of Nb1+αS2 sulfidation scales

1992 ◽  
Vol 50 (1) ◽  
pp. 38-39
Author(s):  
Chuxin Zhou ◽  
L. W. Hobbs
Keyword(s):  
Stacking Faults ◽  
Rhombohedral Structure ◽  
Stacking Sequence ◽  
Defect Structures ◽  
X Ray Diffraction ◽  
X Ray ◽  
Plane Normal ◽  
Lower Case ◽  
Sulfur Layer ◽  
Two Phases

One of the major purposes in the present work is to study the high temperature sulfidation properties of Nb in severe sulfidizing environments. Kinetically, the sulfidation rate of Nb is satisfactorily slow, but the microstructures and non-stoichiometry of Nb1+αS2 challenge conventional oxidation/sulfidation theory and defect models of non-stoichiometric compounds. This challenge reflects our limited knowledge of the dependence of kinetics and atomic migration processes in solid state materials on their defect structures.Figure 1 shows a high resolution image of a platelet from the middle portion of the Nb1+αS2 scale. A thin lamellar heterogeneity (about 5nm) is observed. From X-ray diffraction results, we have shown that Nb1+αS2 scale is principally rhombohedral structure, but 2H-NbS2 can result locally due to stacking faults, because the only difference between these 2H and 3R phases is variation in the stacking sequence along the c axis. Following an ABC notation, we use capital letters A, B and C to represent the sulfur layer, and lower case letters a, b and c to refer to Nb layers. For example, the stacking sequence of 2H phase is AbACbCA, which is a ∼12Å period along the c axis; the stacking sequence of 3R phase is AbABcBCaCA to form an ∼18Å period along the c axis. Intergrowth of these two phases can take place at stacking faults or by a shear in the basal plane normal to the c axis.

Role of Aluminium on the Microstructure and Corrosion Behaviour of Magnesium Prepared by Powder Metallurgy Method

2020 ◽  
Vol 17 (3) ◽  
pp. 8206-8213
Author(s):  
J. Alias
Keyword(s):  
Corrosion Resistance ◽  
Powder Metallurgy ◽  
Corrosion Behaviour ◽  
Corrosion Current ◽  
Optical Microscope ◽  
High Reactivity ◽  
Aluminium Content ◽  
Powder Metallurgy Method ◽  
X Ray Diffraction ◽  
Promising Development

Much research on magnesium (Mg) emphasises creating good corrosion resistance of magnesium, due to its high reactivity in most environments. In this study, powder metallurgy (PM) technique is used to produce Mg samples with a variation of aluminium (Al) composition. The effect of aluminium composition on the microstructure development, including the phase analysis was characterised by optical microscope (OM), scanning electron microscopy (SEM) and x-ray diffraction (XRD). The mechanical property of Mg sample was performed through Vickers microhardness. The results showed that the addition of aluminium in the synthesised Mg sample formed distribution of Al-rich phases of Mg17Al12, with 50 wt.% of aluminium content in the Mg sample exhibited larger fraction and distribution of Al-rich phases as compared to the 20 wt.% and 10 wt.% of aluminium content. The microhardness values were also increased at 20 wt.% and 50 wt.% of aluminium content, comparable to the standard microhardness value of the annealed Mg. A similar trend in corrosion resistance of the Mg immersed in 3.5 wt.% NaCl solution was observed. The corrosion behaviour was evaluated based on potentiodynamic polarisation behaviour. The corrosion current density, icorr, is observed to decrease with the increase of Al composition in the Mg sample, corresponding to the increase in corrosion resistance due to the formation of aluminium oxide layer on the Al-rich surface that acted as the corrosion barrier. Overall, the inclusion of aluminium in this study demonstrates the promising development of high corrosion resistant Mg alloys.

scholarly journals X-ray and Neutron Study on the Structure of Hydrous SiO2 Glass up to 10 GPa

Minerals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 84 ◽  
Author(s):  
Satoru Urakawa ◽  
Toru Inoue ◽  
Takanori Hattori ◽  
Asami Sano-Furukawa ◽  
Shinji Kohara ◽  
...  
Keyword(s):  
Oxide Glasses ◽  
Void Space ◽  
X Ray Diffraction ◽  
Amorphous Sio2 ◽  
Sio2 Glass ◽  
X Ray ◽  
X Ray Scattering ◽  
Medium Range ◽  
Two Phases ◽  
A Minor

The structure of hydrous amorphous SiO2 is fundamental in order to investigate the effects of water on the physicochemical properties of oxide glasses and magma. The hydrous SiO2 glass with 13 wt.% D2O was synthesized under high-pressure and high-temperature conditions and its structure was investigated by small angle X-ray scattering, X-ray diffraction, and neutron diffraction experiments at pressures of up to 10 GPa and room temperature. This hydrous glass is separated into two phases: a major phase rich in SiO2 and a minor phase rich in D2O molecules distributed as small domains with dimensions of less than 100 Å. Medium-range order of the hydrous glass shrinks compared to the anhydrous SiO2 glass by disruption of SiO4 linkage due to the formation of Si–OD deuterioxyl, while the response of its structure to pressure is almost the same as that of the anhydrous SiO2 glass. Most of D2O molecules are in the small domains and hardly penetrate into the void space in the ring consisting of SiO4 tetrahedra.

A Lightweight Formalism for Reference Lifetimes and Borrowing in Rust

2021 ◽  
Vol 43 (1) ◽  
pp. 1-73
Author(s):  
David J. Pearce
Keyword(s):  
Memory Management ◽  
Programming Model ◽  
Type System ◽  
Control Flow ◽  
Two Phase ◽  
Type Checking ◽  
Strong Focus ◽  
Reference Implementation ◽  
Two Phases ◽  
Complex Features

Rust is a relatively new programming language that has gained significant traction since its v1.0 release in 2015. Rust aims to be a systems language that competes with C/C++. A claimed advantage of Rust is a strong focus on memory safety without garbage collection. This is primarily achieved through two concepts, namely, reference lifetimes and borrowing . Both of these are well-known ideas stemming from the literature on region-based memory management and linearity / uniqueness . Rust brings both of these ideas together to form a coherent programming model. Furthermore, Rust has a strong focus on stack-allocated data and, like C/C++ but unlike Java, permits references to local variables. Type checking in Rust can be viewed as a two-phase process: First, a traditional type checker operates in a flow-insensitive fashion; second, a borrow checker enforces an ownership invariant using a flow-sensitive analysis. In this article, we present a lightweight formalism that captures these two phases using a flow-sensitive type system that enforces “ type and borrow safety .” In particular, programs that are type and borrow safe will not attempt to dereference dangling pointers. Our calculus core captures many aspects of Rust, including copy- and move-semantics, mutable borrowing, reborrowing, partial moves, and lifetimes. In particular, it remains sufficiently lightweight to be easily digested and understood and, we argue, still captures the salient aspects of reference lifetimes and borrowing. Furthermore, extensions to the core can easily add more complex features (e.g., control-flow, tuples, method invocation). We provide a soundness proof to verify our key claims of the calculus. We also provide a reference implementation in Java with which we have model checked our calculus using over 500B input programs. We have also fuzz tested the Rust compiler using our calculus against 2B programs and, to date, found one confirmed compiler bug and several other possible issues.

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