scholarly journals Isokinetic Analysis of Fe41Co7Cr15Mo14Y2C15B6 Bulk Metallic Glass: Effect of Minor Copper Addition

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3704
Author(s):  
Parisa Rezaei-Shahreza ◽  
Amir Seifoddini ◽  
Saeed Hasani ◽  
Zahra Jaafari ◽  
Agata Śliwa ◽  
...  

In the present study, (Fe41Co7Cr15Mo14Y2C15B6)100−xCux (x = 0, 0.25 and 0.5 at.%) amorphous alloys were prepared by copper-mold casting. To clarify the effect of the minor addition of copper on the mechanism of nucleation and growth during the crystallization process, an isokinetic analysis was performed. The activation energies (E) of the various crystallization stages were calculated by using theoretical models including Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), Augis–Bennett and Gao–Wang methods. In addition, Augis–Bennett, Gao–Wang and Matusita methods were used to investigate the nucleation and growth mechanisms and to determine other kinetic parameters including Avrami exponent (n), the rate constant (Kp) and dimensionality of growth (m). The obtained results revealed that the activation energy—as well as thermal stability—was changed with minor addition of copper. In addition, the obtained Avrami exponent values were confirmed by Johnson–Mehl–Avrami–Kolmogorov (JMAK) method. The research findings demonstrated that the value of Avrami exponent is changed with minor addition of copper, so that the Avrami exponents of all crystallization stages, except the second peak for copper-free amorphous alloy, were equal to integer values ranging from two to four, indicating that the growth mechanisms were controlled by interface. Moreover, the kinetic parameters of n and b for all peaks were increased by an increase in crystallization temperature, which can be attributed to the increase in the nucleation rate.

Author(s):  
L.R. Wallenberg ◽  
J.-O. Bovin ◽  
G. Schmid

Metallic clusters are interesting from various points of view, e.g. as a mean of spreading expensive catalysts on a support, or following heterogeneous and homogeneous catalytic events. It is also possible to study nucleation and growth mechanisms for crystals with the cluster as known starting point.Gold-clusters containing 55 atoms were manufactured by reducing (C6H5)3PAuCl with B2H6 in benzene. The chemical composition was found to be Au9.2[P(C6H5)3]2Cl. Molecular-weight determination by means of an ultracentrifuge gave the formula Au55[P(C6H5)3]Cl6 A model was proposed from Mössbauer spectra by Schmid et al. with cubic close-packing of the 55 gold atoms in a cubeoctahedron as shown in Fig 1. The cluster is almost completely isolated from the surroundings by the twelve triphenylphosphane groups situated in each corner, and the chlorine atoms on the centre of the 3x3 square surfaces. This gives four groups of gold atoms, depending on the different types of surrounding.


Author(s):  
S. Q. Xiao ◽  
S. Baden ◽  
A. H. Heuer

The avian eggshell is one of the most rapidly mineralizing biological systems known. In situ, 5g of calcium carbonate are crystallized in less than 20 hrs to fabricate the shell. Although there have been much work about the formation of eggshells, controversy about the nucleation and growth mechanisms of the calcite crystals, and their texture in the eggshell, still remain unclear. In this report the microstructure and microchemistry of avian eggshells have been analyzed using transmission electron microscope (TEM) and energy dispersive spectroscopy (EDS).Fresh white and dry brown eggshells were broken and fixed in Karnosky's fixative (kaltitanden) for 2 hrs, then rinsed in distilled H2O. Small speckles of the eggshells were embedded in Spurr medium and thin sections were made ultramicrotome.The crystalline part of eggshells are composed of many small plate-like calcite grains, whose plate normals are approximately parallel to the shell surface. The sizes of the grains are about 0.3×0.3×1 μm3 (Fig.l). These grains are not as closely packed as man-made polycrystalline metals and ceramics, and small gaps between adjacent grains are visible indicating the absence of conventional grain boundaries.


2021 ◽  
pp. 147332502199466
Author(s):  
Steffany Sloan ◽  
Jacquelyn J Benson

Transgender older adults have been subject to life-long stigma and marginalization, resulting in significant social and health consequences. Despite these challenges, this population commonly reports thriving in later life. In order to attend to nuanced experiences of older transgender adults, theoretical models of successful aging must reflect complexities presented by gender minority status. In order to address theoretical gaps, a systematic qualitative meta-synthesis was conducted to summarize findings across the body of qualitative transgender aging research. Findings indicated that transgender older adults conceptualize successful aging through the process of embracing gender identity. Themes were identified to conceptualize successful transgender aging such as gender expression, shedding internalized stigma, and championing a resilience mindset. Implications for social work practice are provided, suggesting a more comprehensive understanding of both challenges and resilience factors amongst the aging transgender population.


2011 ◽  
Vol 317-319 ◽  
pp. 42-47
Author(s):  
Li Fang Zhang ◽  
Yong Chang Liu

By fitting the calculated transformed fraction according to developed phase-transformation model to the experimental data obtained by differential dilatometry, the kinetic characteristics of the austenitization process in T91 steels have been investigated. According to the kinetic parameters fitted, we recognize that the nucleation and growth of austenite grain are mainly controlled by the diffusion of carbon in ferritic and austenite respectively. In addition, by increasing the diffusion active energy of carbon in austenite, carbides hinder the motion of interface and thus refine austenite grain.


Carbon ◽  
2020 ◽  
Vol 161 ◽  
pp. 17-24 ◽  
Author(s):  
Yuanyuan Jiang ◽  
Zhanqiu Tan ◽  
Genlian Fan ◽  
Zhibo Zhang ◽  
Ding-Bang Xiong ◽  
...  

2000 ◽  
Author(s):  
Zongyan He ◽  
Jack G. Zhou

Abstract A new solid free-form fabrication (SFF) technique, named Physical and Chemical Liquid Deposition (P/CLD), is introduced in this paper, and then several key technical problems are stated. In order to solve these problems, theoretical models to describe the nucleation and growth of deposits in PLD, the chemical dynamic process in CLD, and the heat transfer in P/LCD are studied. To determine the heat transfer parameters, some experiments are designed and experimental results are presented.


2000 ◽  
Vol 3 (2) ◽  
pp. 334-343
Author(s):  
I. Olivier ◽  
M. Fletcher

With the current focus on establishing long-tenn customer relationships, the enhancement of the entire shopping experience and the role of atmosphere and the emotional reactions it elicits, are becoming increasingly important. Determining the factors that contribute to the creation of pleasant or unpleasant shopping experiences can influence future strategic planning. The focus of this study falls on the way that the physical environmental factors of a store, more specifically the environmental odour, affect consumers' emotional responses. This is discussed on the basis of environmental psychology, using certain research findings as well as theoretical models to shed more light on this topic.


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