68 research outputs found
Thermodynamic Modelling of the Mg-Al-Ca System
In this study, the ternary Mg-Al-Ca phase diagram was constructed by combining the three constituent binary systems of Mg-Al, Al-Ca and Mg-Ca. The Mg-Al system is taken from COST 507 database. The thermodynamic descriptions of the Mg-Ca and Al-Ca systems are obtained by modelling the Gibbs energy of all phases as a function of composition and temperature. The model parameters were
optimized by minimizing Gibbs energy considering phase equilibria and thermodynamic data available in the literature. A self-consistent thermodynamic database was constructed with the optimized parameters of the three subsystems. The binary phase diagrams, their thermodynamic properties, the ternary phase diagram and the critical points were calculated from this database and compared with experimental results from the literature
Intrinsic magnetic properties of Ce 2 (Fe, Co) 14 B and its modifications by Ni and Cu
The intrinsic magnetic properties of Ce2Fe14-xCoxB (x ≤ 4.76) are studied at 25 °C using key alloys annealed at 900 °C for 25 days. The saturation magnetization (Ms) and the Curie temperature (Tc) of Ce2Fe14-xCoxB increase with Co content. However, the anisotropy field (Ha) of Ce2Fe14-xCoxB diminishes precipitously with Co content. The process of crystal structure refinemen indicates that the saturation magnetization of Ce2Fe14-xCoxB is related to the site occupancy of Co atoms at different Fe atomic sites. Co atoms prefer to occupy 8j2 site, followed by 16k2, 4e and 16k1 sites sequentially. Moreover, Co atoms occupying 8j2 site are more effective leading to an increase in the Ms. The individual effects of Ni or Cu on the intrinsic magnetic properties of Ce2Fe12.98-xCo1.02NixB and Ce2Fe12.98-yCo1.02CuyB are evaluated. The maximum solid solubilities of Ni and Cu in Ce2Fe12.98Co1.02B at 900 °C are found to be 8 at.% and 0.8 at.%, respectively. Ni or Cu enhances Tc, but decreases both Ms and Ha of Ce2Fe12.98Co1.02B. The paper also discussed the combined effects of Ni and Cu on the intrinsic magnetic properties of Ce2Fe12.98Co1.02B. The Ms of Ce2Fe12.98-x-yCo1.02NixCuyB (0 ≤ x ≤ 0.41, y ≈ 0.119) increases after doping with both Ni and Cu, reaching around 155 emu/g. Meanwhile, the Ha and the Tc are measured to be near 24 kOe and 280 °C, respectively
Experimental Investigation of the Ce-Mg-Mn Isothermal Section at 723 K (450°C) via Diffusion Couples Technique
The isothermal section of the Ce-Mg-Mn phase diagram at 723 K (450°�C) was established
experimentally by means of diffusion couples and key alloys. The phase relationships in the
complete composition range were determined based on six solid–solid diffusion couples and
twelve annealed key alloys. No ternary compounds were found in the Ce-Mg-Mn system at
723 K (450°C). X-ray diffraction and energy-dispersive X-ray spectroscopy spot analyses were used for phase identification. EDS line-scans, across the diffusion layers, were performed to determine the binary and ternary homogeneity ranges. Mn was observed in the diffusion couples
and key alloys microstructures as either a solute element in the Ce-Mg compounds or as a pure element, because it has no tendency to form intermetallic compounds with either Ce or Mg. The fast at. interdiffusion of Ce and Mg produces several binary compounds (CexMgy) during the diffusion process. Thus, the diffusion layers formed in the ternary diffusion couples were similar to those in the Ce-Mg binary diffusion couples, except that the ternary diffusion couples contain layers of Ce-Mg compounds that dissolve certain amount of Mn. Also, the ternary diffusion
couples showed layers containing islands of pure Mn distributed in most diffusion zones. As a result, the phase boundary lines were pointing toward Mn-rich corner, which supports the tendency of Mn to be in equilibrium with all the phases in the system
Phase Equilibria of the Ce-Mg-Zn Ternary System at 300 °C
The isothermal section of the Ce-Mg-Zn system at 300 °C was experimentally established in the full composition range via diffusion multiple/couples and key alloys. Annealed key alloys were used to confirm the phase equilibria obtained by diffusion multiple/couples and to determine the solid solubility ranges. Spot analysis was carried out, using wavelength dispersive X-ray spectroscopy (WDS), to identify the composition of the observed phases. The composition profiles were obtained using WDS line-scans across the diffusion zones. X-ray diffraction (XRD) was performed to identify the phases in the annealed alloys and to confirm the WDS results. Eight ternary compounds, in the Ce-Mg-Zn isothermal section at 300 °C, were observed from 45–80 at.% Zn. These are:
Ï„1 (Ce6Mg3Zn19), Ï„2 (CeMg29Zn25), Ï„3 (Ce2Mg3Zn3), Ï„4 (CeMg3Zn5), Ï„5 (CeMg7Zn12),
τ6 (CeMg2.3−xZn12.8+x; 0 ≤ x ≤ 1.1), τ7 (CeMgZn4) and τ8 (Ce(Mg1−yZny)11; 0.096 ≤ y ≤ 0.43). The ternary solubility of Zn in the Ce-Mg compounds was found to increase with a decrease in Mg concentration. Accordingly, the ternary solid solubility of Zn in CeMg12 and CeMg3 was measured as 5.6 and 28.4 at.% Zn, respectively. Furthermore, the CeMg and CeZn showed a complete solid solubility. The complete solubility was confirmed by a diffusion couple made from alloys containing CeMg and CeZn compounds
Binary Phase Diagrams and Thermodynamic Properties of Silicon and Essential Doping Elements (Al, As, B, Bi, Ga, In, N, P, Sb and Tl)
Fabrication of solar and electronic silicon wafers involves direct contact between solid, liquid and gas phases at near equilibrium conditions. Understanding of the phase diagrams and thermochemical properties of the Si-dopant binary systems is essential for providing processing conditions and for understanding the phase formation and transformation. In this work, ten Si-based binary phase diagrams, including Si with group IIIA elements (Al, B, Ga, In and Tl) and with group VA elements (As, Bi, N, P and Sb), have been reviewed. Each of these systems has been critically discussed on both aspects of phase diagram and thermodynamic properties. The available experimental data and thermodynamic parameters in the literature have been summarized and assessed thoroughly to provide consistent understanding of each system. Some systems were re-calculated to obtain a combination of the best evaluated phase diagram and a set of optimized thermodynamic parameters. As doping levels of solar and electronic silicon are of high technological importance, diffusion data has been presented to serve as a useful reference on the properties, behavior and quantities of metal impurities in silicon. This paper is meant to bridge the theoretical understanding of phase diagrams with the research and development of solar-grade silicon production, relying on the available information in the literature and our own analysis
Experimental Investigation of the Mg-Nd-Zn Isothermal Section at 300 °C
The Mg-Nd-Zn isothermal section at 300 °C was established in the full composition range using diffusion couples and equilibrated key alloys. Microstructural characterization was carried out using WDS, XRD, and metallographic methods. The homogeneity ranges of the binary and ternary compounds were determined by WDS analysis. Six ternary compounds were observed in the Mg-Nd-Zn system at 300 °C. These are: τ1(Nd5Mg21+xZn45−x; 0 ≤ x ≤ 4), τ2 (Nd5Mg3+yZn25−y; 0 ≤ y ≤ 1), τ3 (NdMg1+zZn2−z; 0 ≤ z ≤ 0.44), τ4 (Mg40Nd5Zn55), τ5 (Mg22–23.5Nd15.5–17.5Zn59.1–61.8), and τ6 (Nd2(Mg,Zn)23). τ5 was found to have a homogeneity range of 22.0–23.5 atom % Mg, 15.5–17.6 atom % Nd and 59.1–61.8 atom % Zn and τ6 was found to have 54.1–61.3 atom % Mg at a constant Nd of 8.0 atom %. The ternary solubility of Zn in Mg-Nd compounds was found to increase with the decrease in Mg concentration. Accordingly, (Mg41Nd5) was found to have an extended solubility of 3.1 atom % Zn, whereas (Mg3Nd) was found to have 30.0 atom % Zn. MgNd was found to have a complete substitution of Mg by Zn. The maximum solid solubility of Zn in α-Mg was measured as 4.8 atom % Zn
Magnetic force microscopic study of Ce 2 (Fe, Co) 14 B, and its modifications by Ni and Cu
The domain width and domain wall energy of the Ce2Fe14-xCoxB solid solution are studied for the first time in this work. The influence of Co content on these properties has been analyzed with the aid of magnetic force microscopy using diffusion couple and key alloys. The domain widths of Ce2Fe14-xCoxB decreased with increasing Co content at about 0.02 μm per 1 at.% Co. In Ce2Fe14-xCoxB, phase shift, domain width and saturation magnetization are related in a way that lower average domain width is associated with higher phase shift and higher saturation magnetization. The highest domain wall energy of Ce2Fe14-xCoxB is measured as 31.7 erg/cm2 after dissolving 14 at.% Co (x=2.38). The effects of Ni and Cu on the domain width and domain wall energy of Ce2Fe14-xCoxB (x=1.02) are also studied and reported using response surfaces. The domain width and domain wall energy of this solid solution increased after doping with 1 at.% Ni at constant Co content of 6 at.%, measuring 1.39 μm for domain width and 33.4 erg/cm2 for domain wall energy. Both properties were determined as 0.71 μm and 18.6 erg/cm2, respectively, after doping with 0.8 at.% Cu, while keeping Co content constant at 6 at.%. When Ce2Fe14-xCoxB (x=1.02) is doped with both Ni (1 at.%) and Cu (0.8 at.%), the domain width and domain wall energy measured 0.99 μm and 33.8 erg/cm2, respectively
Essential Magnesium Alloys Binary Phase Diagrams
Magnesium-based alloys are becoming a major industrial material for structural applications because of their potential weight saving characteristics. All the commercial Mg alloys like AZ, AM, AE, EZ, ZK etc. series are multicomponent and hence it is important to understand the phase relations of the alloying elements with Mg. In this work, eleven essential Mg-based binary systems including Mg-Al/Zn/Mn/Ca/Sr/Y/Ni/Ce/Nd/Cu/Sn have been reviewed. Each of these systems has been discussed critically on the aspects of phase diagram and thermodynamic properties.All the available experimental data has been summarized and assessed critically to provide detailed understanding of the system. The phase diagrams are calculated based on the most up to date optimized parameters. Critical information of the phase diagram both as composition and temperature are shown on the figures. The thermodynamic model parameters for all the systems except Mg-Nd, have been summarized in Tables. These parameters are important for further development of the alloys into the multicomponent systems. The crystallographic information of all the intermetallic compounds of different binary systems is also provided. Also,the heat of formation of the intermetallic compounds for each system obtained from experimental, first principle calculations and CALPHAD optimizations are provided.In addition re-optimization of the Mg-Y system has been done in this work since new experimental data showed wider solubility of the intermetallic compounds
Experimental Demonstration of Entrance/Exit Effects on the Permeability Measurements of Porous Materials
Peer reviewed: YesNRC publication: Ye
Experimental study of the Ca–Mg–Zn system using diffusion couples and key alloys
Nine diffusion couples and 32 key samples were prepared to map the phase diagram of the Ca–Mg–Zn system. Phase relations and solubility limits were determined for binary and ternary compounds using scanning electron microscopy, electron probe microanalysis and x-ray diffraction (XRD). The crystal structure of the ternary compounds was studied by XRD and electron backscatter diffraction. Four ternary intermetallic (IM) compounds were identified in this system: Ca3MgxZn15−x (4.6≤x≤12 at 335 °C, IM1), Ca14.5Mg15.8Zn69.7 (IM2), Ca2Mg5Zn13 (IM3) and Ca1.5Mg55.3Zn43.2 (IM4). Three binary compounds were found to have extended solid solubility into ternary systems: CaZn11, CaZn13 and Mg2Ca form substitutional solid solutions where Mg substitutes for Zn atoms in the first two compounds, and Zn substitutes for both Ca and Mg atoms in Mg2Ca. The isothermal section of the Ca–Mg–Zn phase diagram at 335 °C was constructed on the basis of the obtained experimental results. The morphologies of the diffusion couples in the Ca–Mg–Zn phase diagram at 335 °C were studied. Depending on the terminal compositions of the diffusion couples, the two-phase regions in the diffusion zone have either a tooth-like morphology or contain a matrix phase with isolated and/or dendritic precipitates
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