The nucleation and growth mechanism of electrodeposited Ni−W alloy were investigated.Cyclic voltammetry(CV)and chronoamperometry(CA)were used to examine the electrochemical behavior and nucleation mechanism of the ele...The nucleation and growth mechanism of electrodeposited Ni−W alloy were investigated.Cyclic voltammetry(CV)and chronoamperometry(CA)were used to examine the electrochemical behavior and nucleation mechanism of the electrodeposited Ni−W alloy.The nucleation type and kinetic parameters of the electrodeposited Ni−W alloy were obtained from the CA analysis results.SEM,AFM,and TEM were also used to investigate the nucleation and growth process of the electrodeposition of Ni−W alloy.The results demonstrate that the nucleation and initial stages of the growth phase of the Ni−W alloy undergo the formation,movement,and aggregation of atoms,single crystals,and nanoclusters.When the size of single crystal increases up to approximately 10 nm and the average size of the crystal granules is approximately 68 nm,they no longer grow.Increasing the applied potential increases the number of nuclei but does not affect the size of the final crystal granules.Therefore,the electrodeposited Ni−W alloy shows a nanocrystalline structure.展开更多
An accurate four-line ac electrical resistance measurement (ERM)apparatus was developed. By using the ERM the crystallization kinetics of amorphous Ni80P20, FeZr2, Fe86B14 alloys were investigated. The experimental re...An accurate four-line ac electrical resistance measurement (ERM)apparatus was developed. By using the ERM the crystallization kinetics of amorphous Ni80P20, FeZr2, Fe86B14 alloys were investigated. The experimental results show that the ERM can identify the early stage of crystallization in amorphous alloys. The ERM detects a crystallization temperature range obviously wider than the DSC does, indicating that the ERM is more sensitive to the structure evolution in crystallization. For the eutectic or polymorphic crystallization, three distinct processes can be identified from the measured resistance variation: (i) crystal nucleation, (ii) subsequent growth of crystal nuclei, and (iii) coarsening of the crystallites. In the early stage of the primary crystallization, the ERM results reflect the nucleation information as well.展开更多
Understanding the structural characteristics and growth mechanism（s） are essen-tial for generating core-shell nano-heterostructures with distinctive properties. Especially in lanthanide-based nanocrystals, rational ...Understanding the structural characteristics and growth mechanism（s） are essen-tial for generating core-shell nano-heterostructures with distinctive properties. Especially in lanthanide-based nanocrystals, rational design of the core-shell composition can be utilized to enhance/tune the optical properties of the final nanostructure, or can be used to integrate multiple functional applications （e.g., luminescent/magnetic）. In this article, we review the progress in our current understanding of the epitaxial shell growth in sodium lanthanide fluoride （NaLnF4） nanocrystals. In order to understand epitaxial shell growth the core nanocrystals have to be uniform, and to date the synthesis of high quality near uniform size/shape dispersion controlled synthesis of lanthanide-based nanocrystals has been achieved mainly with this class of nanocrystals. The progress in core-shell synthesis and the epitaxial shell growth mechanism in this class of nanocrystals （NaLnF4） are reviewed, and a general perspective is provided on the core-shell morphology based on different characterization techniques. While there has been tremendous progress in studying the impact of core-shell structures in various functional applications, this review also highlights, in our view, the still limited understanding of ways to control the core-shell morphology and it emphasizes some important, unanswered questions that remain to be addressed to maximize their performance.展开更多
基金financial support from the Science and Technology Project of Hunan Province,China(No.2018TP1012)。
文摘The nucleation and growth mechanism of electrodeposited Ni−W alloy were investigated.Cyclic voltammetry(CV)and chronoamperometry(CA)were used to examine the electrochemical behavior and nucleation mechanism of the electrodeposited Ni−W alloy.The nucleation type and kinetic parameters of the electrodeposited Ni−W alloy were obtained from the CA analysis results.SEM,AFM,and TEM were also used to investigate the nucleation and growth process of the electrodeposition of Ni−W alloy.The results demonstrate that the nucleation and initial stages of the growth phase of the Ni−W alloy undergo the formation,movement,and aggregation of atoms,single crystals,and nanoclusters.When the size of single crystal increases up to approximately 10 nm and the average size of the crystal granules is approximately 68 nm,they no longer grow.Increasing the applied potential increases the number of nuclei but does not affect the size of the final crystal granules.Therefore,the electrodeposited Ni−W alloy shows a nanocrystalline structure.
基金This work was supported by the Chinese Academy of Sciences and the National Natural Science Foundation of China (Grant No. 59625101).
文摘An accurate four-line ac electrical resistance measurement (ERM)apparatus was developed. By using the ERM the crystallization kinetics of amorphous Ni80P20, FeZr2, Fe86B14 alloys were investigated. The experimental results show that the ERM can identify the early stage of crystallization in amorphous alloys. The ERM detects a crystallization temperature range obviously wider than the DSC does, indicating that the ERM is more sensitive to the structure evolution in crystallization. For the eutectic or polymorphic crystallization, three distinct processes can be identified from the measured resistance variation: (i) crystal nucleation, (ii) subsequent growth of crystal nuclei, and (iii) coarsening of the crystallites. In the early stage of the primary crystallization, the ERM results reflect the nucleation information as well.
文摘Understanding the structural characteristics and growth mechanism（s） are essen-tial for generating core-shell nano-heterostructures with distinctive properties. Especially in lanthanide-based nanocrystals, rational design of the core-shell composition can be utilized to enhance/tune the optical properties of the final nanostructure, or can be used to integrate multiple functional applications （e.g., luminescent/magnetic）. In this article, we review the progress in our current understanding of the epitaxial shell growth in sodium lanthanide fluoride （NaLnF4） nanocrystals. In order to understand epitaxial shell growth the core nanocrystals have to be uniform, and to date the synthesis of high quality near uniform size/shape dispersion controlled synthesis of lanthanide-based nanocrystals has been achieved mainly with this class of nanocrystals. The progress in core-shell synthesis and the epitaxial shell growth mechanism in this class of nanocrystals （NaLnF4） are reviewed, and a general perspective is provided on the core-shell morphology based on different characterization techniques. While there has been tremendous progress in studying the impact of core-shell structures in various functional applications, this review also highlights, in our view, the still limited understanding of ways to control the core-shell morphology and it emphasizes some important, unanswered questions that remain to be addressed to maximize their performance.
