Ln Xi Research Articles

Oxygen Reduction Reaction Properties of Dry-Process Synthesized Pt-Non PGM Transition Metal Multi-Component Alloys: Influence of Transition Metal Elements

Introduction Multi-component alloys (MCAs) have been attracted much attention in various engineering application fields. [1] By changing numbers of constituent elements (n) as well as their composition ratios (𝑥) of MCAs, the mixing-entropy (ΔSmix = −𝑅∑(𝑖=1→n) 𝑥𝑖 ln 𝑥𝑖) increases with increasing n, resulting in reduced Gibbs free-energy (ΔG = ΔH - TΔS) of the MCAs, which correlates with interesting bulk material’s properties. Furthermore, the MCAs surfaces possess specific chemical properties, for example, high thermodynamic and chemical stabilities, probably caused by the reduced ΔG, that are much different from those of binary alloys, e.g., Pt-Co or Pt-Ni. Therefore, the MCAs surfaces can be applied for novel nano-materials developments, including electrocatalytic materials. [2] Indeed, our previous study for single-crystal surfaces of the MCAs system of Pt and non-PGM Cr-Mn-Fe-Co-Ni (known as Cantor alloy [3]) demonstrates that enhanced oxygen reduction reaction (ORR) activity at a pristine state and, furthermore, electrochemical structural stability even through the potential cycle (PC)-loading. [4] Thermodynamical and chemical properties of the MCAs surfaces are, in general, a superposition of specific properties of the constituent elements and newly emerging properties that stemming from multi-component alloying. Therefore, catalytic influences of the multiple alloying-elements on ORR properties (activity and structural stability) of Pt-containing MCAs (referred to as Pt-MCAs) surfaces are much complicated, due mainly to the sluggish diffusion and segregation behaviors of the constituent elements. Thus, optimizing the constituent elements (kinds and n) and their composition ratios (𝑥) at the surface vicinity is surely essential for considering an application of the MCAs as practical ORR catalysts. In this study, we synthesized Pt-MCAs on Pt(111) substrate surface with various n and kinds of the constituent elements by controlling vacuum-deposition amounts of the elements and conducted fundamental investigations aimed for high performance cathode alloy catalyst’s developments of polymer electrolyte membrane fuel cells. Experimental In this study, we focused on equi-composition-ratio of the MCAs by picking up 2~5 elements of Cr, Mn, Fe, Co, and Ni as alloying elements of Pt. 10 monolayer (ML)-thick (1 ML = ca. 0.3 nm) MCAs layer was first deposited on the surface-cleaned Pt(111) substrate by using an arc-plasma deposition method at 300 K, and subsequently annealed in vacuum at 773 K for 30 min. Then, 4 ML-thick Pt layer was deposited on the MCAs layer at 300 K and post-annealed at 623 K in vacuum. The samples thus prepared are designated as Pt/MCAs/Pt(111). The atomic-level micro-structures and composition ratios of the surface-vicinity of resulting Pt/MCAs/Pt(111) were characterized by cross-sectional STEM-EDS and XPS. CVs and LSVs were conducted in N2-purged and O2-saturated 0.1 M HClO4 by using an RDE apparatus. ORR activity was evaluated from j k values estimated at 0.9 V vs. RHE by using Koutecky-Levich equation and structural stability (ORR durability) was discussed based upon the activity transitions during applying 5,000 potential cycles (PCs) of 0.6(3s)‐1.0(3s) V vs. RHE in O2 saturated 0.1 M HClO4 at room temperature. Results and Discussion The ORR activity trends under applying the PC loading (a), initial CVs (b), and XPS-estimated surface compositions of Pt/MCAs/Pt(111) are summarized in Fig. 1(a-c), where Cr-Mn-Fe-Co-Ni, Mn-Fe-Co-Ni, Cr-Fe-Co-Ni, and Fe-Co-Ni are adopted for the MCAs. Notably, the ORR activity of Cr containing Pt/Cr-Fe-Co-Ni/Pt(111) (green) decreased remarkably up to 2,000 PCs, compared to Cr-less Pt/Mn-Fe-Co-Ni/Pt(111) (red), Pt/Fe-Co-Ni/Pt(111) (yellow), and both Cr and Mn containing Pt/Cr-Mn-Fe-Co-Ni(Cantor alloy)/Pt(111) (blue). Furthermore, Pt/Cr-Fe-Co-Ni/Pt(111) exhibited increased electric double layer charge in the potential region of 0.4 to 0.6 V at the pristine state (b). Additionally, XPS-estimated relatively smaller and larger composition ratios of the Pt and Cr, respectively, among the tested Pt/MCAs/Pt(111) (c), suggesting that Cr of the MCAs preferentially diffuses and segregates at the surface-vicinity through the heat treatment process of the sample fabrication, which might cause severe decrease in ORR activity at the early stage of the PCs loading (up to 2,000 PCs). [5] At the meeting, correlations between the ORR properties and atomic-level microstructures of Pt/MCAs/Pt(111) surfaces will be discussed in detail. Acknowledgement This study was supported by new energy and industrial technology development organization (NEDO) of Japan, JST SPRING, Grant Number JPMJJSP2114 (Y.C.) and Grant-in-Aid for JSPS Fellows (Y.C.).

Cost and Land Functions for Wastewater Treatment Projects: Typical Simple Linear Regression versus Fuzzy Linear Regression

This paper analyzes cost data pertinent to the municipal wastewater treatment plants (MWTP) in Greece. First, data have been collected with onsite visits and contain the land size necessary for a MWTP, the construction cost, and the operation and maintenance cost of existing wastewater treatment facilities. Second, they come from analytical budgeting of natural wastewater treatment system units. Twelve equations of the form ln Yi = A0i + A1i ln Xi are estimated both with ordinary least squares (OLS) and fuzzy linear regression (FLR). The root mean square error and the mean absolute error are used as fitting measures for the comparison of the OLS with the fuzzy estimations. It is shown that the FLR did produce very similar estimates but slightly inferior to those of OLS in most of the cases for these particular datasets.

Effect of smolt size on postrelease survival of hatchery-reared masu salmon Oncorhynchus masou

SUMMARY: The relationship between mean weights of hatchery-reared masu salmon Oncorhynchus masou smolts at release and the subsequent recovery rates by coastal commercial fisheries in Hokkaido, northern Japan, was investigated using the maximum likelihood method. A strongly positive correlation was observed, showing smolts with a mean of 32.6 g obtained an approximately 20-fold recovery rate of those with a mean of 14.8 g. The model with log-transformed independent variable (Yi = –11.237 + 4.239 ln Xi) was selected as the most parsimonious model to represent the release size (Xi) and recovery rate (Yi) relationship.

Kinetics of Sr and Nd exchange in silicate liquids: Theory, experiments, and applications to uphill diffusion, isotopic equilibration, and irreversible mixing of magmas

Diffusion coefficients that govern chemical and isotopic exchange of Sr and Nd were determined from compositional profiles developed between juxtaposed anhydrous basaltic and rhyolitic liquids. Analysis of simple diffusion couples involving isotopically enriched and normal tholeiitic basalt and metaluminous rhyolite recover Sr and Nd self‐diffusion coefficients (D*) in the end‐member compositions of contrasting polymerization. Self‐diffusion of Sr is 7 times faster in basaltic melt than rhyolitic melt at 1255°C and 1 GPa, while self‐diffusion of Nd is more than 1 order of magnitude greater in basalt than rhyolite. Also, at these conditions, DSr* is a factor of 3 greater than DNd* in basalt and an order of magnitude greater than DNd* in rhyolite. Variations in DSr* and DNd* with bulk composition and temperature between 1255°–1465°C are described by ln DSr* = −16.25 ‐ (16348/T) + 8.02(0.73 ‐ XSiO2) and ln DNd* = −13.73 ‐ (23875/T) + 14.43(0.73 ‐ XSiO2), where the units of D* are square meters per second, T is temperature in kelvins, and XSiO2 is weight fraction silica. The results of a Boltzmann‐Matano analysis of 87Sr/∑Sr and 144Nd/∑Nd profiles of complex diffusion couples composed of isotopically normal basalt and enriched rhyolite yield diffusion coefficients for intermediate bulk compositions in agreement with interpolated values given by the relationships above. An important feature of the interdiffusion of basaltic and rhyolitic liquids is the equilibration of isotopic composition in advance of chemical homogenization. This behavior is best displayed by Sr in the present experiments and predicted for Nd. In addition, Sr, Nd, and Al show initial periods of uphill diffusion, while other melt components diffuse down their respective concentration gradients leading to chemical homogenization. Despite uphill diffusive effects, the rate of chemical homogenization is slow and approximated by the effective binary diffusion coefficient for silica, that is, ln DSiO2B‐M = −6.70 ‐ (31195/T) + 12.28(0.52 ‐ XSiO2). Chemical fluxes of Sr and Nd are calculated using Darken's (1948) equation, that is, Dic = Di*[1 + (d ln γi/d ln xi)], relating the chemical diffusion coefficient for species i(Dic) defined by Pick's law to the self‐diffusion coefficient (Di*) for the species and the variation in the species’ activity coefficient, γi, with concentration xi along the diffusional pathway. Parameters of the Darken equation are provided in this study and from the literature. Simulations of interdiffusion of basalt and rhyolite quantitatively reproduce salient features of the present experiments including (1) the initial stage of Sr and Nd uphill diffusion into silica‐poor regions of couples followed by back diffusion into silica‐rich regions, (2) strong asymmetry in the evolving Sr and Nd isotopic profiles, and (3) equilibration of isotopic composition in advance of bulk chemical composition. These results are considered in a magmatic context, where intimate blending of magmas during mixing is frustrated by large rheological contrasts and/or insufficient exposure time. Time‐dependent diffusional exchange between mingling magmas leads to covariations in chemical and isotopic compositions that differ markedly from the expectations of bulk mixing. Examples presented offer alternative interpretations for the compositional relationships found among magmatic rocks of hybrid origin.

Is mixing a thermodynamic process?

Mixing processes exist with positive entropy change and negative free energy change. However, the idea that the irreversibility of the mixing processes is responsible for the so-called free energy and entropy of mixing is faulty. The mixing, as well as the demixing processes may be associated with either reversible or irreversible phenomena, depending on the particular conditions. For ideal gases, the word ‘‘mixing’’ in the terms ‘‘mixing entropy’’ and ‘‘mixing free energy’’ may sometimes be used descriptively but never causatively. The quantity −∑ Ni R ln Xi, usually referred to as ‘‘mixing entropy,’’ has nothing to do with the mixing phenomenon. Therefore the terms ‘‘mixing entropy’’ and ‘‘mixing free energy’’ are essentially misconceptions. In fact, it is shown that the process of mixing of ideal gases has, by itself, no relevance to any thermodynamic quantity. Therefore, in a thermodynamical sense, it is a nonprocess. The concepts of assimilation and deassimilation are introduced. It is shown that the ‘‘deassimilation process is essentially irreversible.’’ This should replace the traditional principle that ‘‘the mixing process is essentially irreversible.’’

Levene's Test for Relative Variation

Forms of Levene's test for evaluating relative variation (univariate) are compared by simulation, along with the F-test of ratios of squared coefficients of variation, the F-test of ratios of variances of logarithms, and Bartlett's test on logarithms. Only the Levene's tests using the medians were always robust. These consisted of transforming each of a set of sample variates Xi to Yi = | Xi − Md(Xi) | /Md(Xi) or to Yi = | In Xi − Md(ln Xi) | for comparison by ANOVA, where the Md's represent the medians. The use of medians with the log transformation was slightly more powerful when the underlying distributions were positively skewed, while the use of the untransformed ratio form of the test was slightly more powerful when the distributions were symmetrical or negatively skewed. Recommendations and some problems that remain are discussed.