Zinc-induced embrittlement in nickel-base superalloys by simulation and experiment

<p>The high cost of Re has driven interest in processes for recovering Re from scrap superalloy parts. In this work thermodynamic modelling is used to study Zn-induced embrittlement of a superalloy and to direct experiments. Treating superalloy powder with Zn vapour reduces the average particle size after milling from approximately m to 0.5–10 m, vs. m for untreated powder. Simulations predict the required treatment time to increase with temperature. Agreement between predictions and experiments suggests that an embrittling liquid forms in less than an hour of Zn vapour treatment between 950–1000 C and partial pressures of Zn between 14–34 kPa (2–5 psi).</p

Platelet Count and Platelet Indices at Various Stages of Normal Pregnancy in Smoking and Non-Smoking Women

Peer Reviewe

Microstructure of alloys (a,c) A6 and (b,d) A7 equilibrated at (a,b) 1273 K and (c,d) 1373 K.

<p>The bright precipitates are Y-containing intermetallics (noted MY).</p

Model parameters and functions for the ternary Al-Co-Cr system.

<p>Only A2, B2, and σ binary parameters are listed in full for their importance, all other binary parameters can be found in the respective binary Al-Co[<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0121386#pone.0121386.ref016" target="_blank">16</a>], Co-Cr[<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0121386#pone.0121386.ref017" target="_blank">17</a>], and Al-Cr[<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0121386#pone.0121386.ref020" target="_blank">20</a>] references as well as the attached database file. Parameters are in units of J/mol-formula.</p><p>Model parameters and functions for the ternary Al-Co-Cr system.</p

Al-Co-Cr Isothermal section at 1273 K.

<p>Shown with phase equilibria data from Ishikawa et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0121386#pone.0121386.ref013" target="_blank">13</a>]: 2-phase (엯), and 3-phase (▿). Experimental phase equilibria data from the present work: 2-phase (●), 3-phase (▲).</p

Cation Disorder Regulation by Microstate Configurational Entropy in Photovoltaic Absorber Materials Cu₂ZnSn(S,Se)₄

Cation disorder plays a major role in the performance deterioration of Cu₂ZnSn­(S,Se)₄ (CZTSSe) photovoltaic (PV) absorbers. Unfortunately the quantitative impact of cation disorder in this material is not well understood. Here, we show that changes in microstate configurational entropy (<i>S</i>_MCE), predicted by a combination of statistical mechanics, density functional theory, and phonon calculations, can quantitatively describe cation disorder and the associated properties in CZTSSe. For example, the predicted critical temperature of the second-order phase transition and the thermal expansion anomaly of CZTS based on <i>S</i>_MCE are in good agreement with experiments. We further reveal that the more separated is the same kind of cations (Cu, Zn, or Sn), the lower the energy of the corresponding microstate will be, implying the maximum entropy probability distribution of cations at high temperatures. It is suggested that the introduction of <i>S</i>_MCE can serve as a framework to quantitatively understand and tailor cation disorder and associated properties for synthesis of the high-quality CZTS-based solar cells

Calculated enthalpies of mixing for solution A2 and B2.

<p>These calculations are based on binary and ternary SQS calculations at 0 K with references taken as bcc-A2 for Al, Co, and Cr.</p><p>Calculated enthalpies of mixing for solution A2 and B2.</p

XRD analysis of selected alloy phase constitutions at 1273 K and 1373 K.

<p>Note that preferential orientations inherent to cast microstructures were still present after annealing. Specimens were rotated in-plane to ensure that all phases were detected.</p

Lateral Versus Vertical Growth of Two-Dimensional Layered Transition-Metal Dichalcogenides: Thermodynamic Insight into MoS₂

Unprecedented interest has been spurred recently in two-dimensional (2D) layered transition metal dichalcogenides (TMDs) that possess tunable electronic and optical properties. However, synthesis of a wafer-scale TMD thin film with controlled layers and homogeneity remains highly challenging due mainly to the lack of thermodynamic and diffusion knowledge, which can be used to understand and design process conditions, but falls far behind the rapidly growing TMD field. Here, an integrated density functional theory (DFT) and calculation of phase diagram (CALPHAD) modeling approach is employed to provide thermodynamic insight into lateral versus vertical growth of the prototypical 2D material MoS₂. Various DFT energies are predicted from the layer-dependent MoS₂, 2D flake-size related mono- and bilayer MoS₂, to Mo and S migrations with and without graphene and sapphire substrates, thus shedding light on the factors that control lateral versus vertical growth of 2D islands. For example, the monolayer MoS₂ flake in a small 2D lateral size is thermodynamically favorable with respect to the bilayer counterpart, indicating the monolayer preference during the initial stage of nucleation; while the bilayer MoS₂ flake becomes stable with increasing 2D lateral size. The critical 2D flake-size of phase stability between mono- and bilayer MoS₂ is adjustable via the choice of substrate. In terms of DFT energies and CALPHAD modeling, the size dependent pressure–temperature–composition (<i>P</i>-<i>T</i>-<i>x</i>) growth windows are predicted for MoS₂, indicating that the formation of MoS₂ flake with reduced size appears in the middle but close to the lower <i>T</i> and higher <i>P</i> “Gas + MoS₂” phase region. It further suggests that Mo diffusion is a controlling factor for MoS₂ growth owing to its extremely low diffusivity compared to that of sulfur. Calculated MoS₂ energies, Mo and S diffusivities, and size-dependent <i>P</i>-<i>T</i>-<i>x</i> growth windows are in good accord with available experiments, and the present data provide quantitative insight into the controlled growth of 2D layered MoS₂

Various properties of the Al, Co, Cr, and the end-members of B2 and σ.

<p>These properties are derived from the energy vs. volume curves using the 4-parameter Birch-Murnaghan EOS. <i>B</i>_<i>0</i> denotes the bulk modulus. The bulk modulus at room temperature of Al, Co, and Cr are also presented, as reported by Kittel [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0121386#pone.0121386.ref056" target="_blank">56</a>]. Other experimental temperatures are shown if known; reported 0 K values are extrapolated from low temperature data.</p><p>Various properties of the Al, Co, Cr, and the end-members of B2 and σ.</p