L-F. Li
,
Z. Zhang
,
and Y Y Li(Cryogenic Laboratory Chinese Academy of Sciences
,
Beijing 100080
,
China)(Institute of Metal Research
,
Chinese Academy of Sciences
,
Shenyang 110015
,
China)
金属学报(英文版)
The microstructure of a fine-grained 16.5mol% CeO2 stabilized tetragonal zirconia polycrystal (Ce-TZP has been investigated by TEM and it is shown that the mi-crostructures of samples fractured at 298, 77 and 4.2 K change significantly. At 298K there is no stress-induced martensite but a few anti-phase boundaries (APBs) in tetragonal (t) parent phase. With a decrease in temperature, monoclinic (m) product or mariensite within retained t-phase appears. The morphologies are characterized as lenticular and block-like at 77 K and as lenticular and butterfly-like at 4.2 K. The relationship between microstructure and mechanical properties is also discassed in this paper.
关键词:
microstructure
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null
,
null
Z. Zhang
金属学报(英文版)
Wavelet transforms (WT) are proposed as an alternative tool to overcome the limita-tions of Fourier transforms (FFT) in the analysis of electrochemical noise (EN) data.The most relevant feature of this method of analysis is its capability of decomposingelectrochemical noise records into different sets of wavelet coefficients, which containinformation about the time scale characteristic of the associated corrosion event. Inthis context, the potential noise fluctuations during the free corrosion of pure alu-minum in sodium chloride solution was recorded and analyzed with wavelet transformtechnique. The typical results showed that the EN signal is composed of distinct typeof events, which can be classified according to their scales, i.e. their time constants.Meanwhile, the energy distribution plot (EDP) can be used as "fingerprints" of ENsignals and can be very useful for analyzing EN data in the future.
关键词:
electrochemical noise
,
null
,
null
,
null
,
null
Z. Zhang
,
C. Cai
,
F.H. Cao
,
Z.N. Gao
,
J.Q. Zhang
,
C.N. Cao
金属学报(英文版)
The corrosion behavior of pure aluminum in neutral 3.0% (mass fraction) sodium chloride (NaCl) solution has been studied using electrochemical impedance spectroscopy (EIS) measurement in conjunction with the scanning electron microscopy (SEM) technique. EIS information on the evolution of pitting corrosion over a period of 15 days has been obtained and analyzed with equivalent circuit technique. The results shown that, during the ensemble constant immersion time, two time constants involved, the high frequency one originated from the protective layer on the corroding surface while the low frequency one from the diffusion process or the corrosion reaction and so on. And there existed a period for oxide film to growth and thickening prior to the commencement of the attacking of chloride ions to the substrate. Meanwhile, good relationship between EIS and the material corrosion type / severity has been obtained, which has been interpreted according to the characteristics of corrosion process such as auto acceleration of pitting corrosion and the protection of local anodic reaction to the area around them.
关键词:
pure aluminum
,
null
,
null
Z. Zhang
,
W.H. Leng
,
J.Q. Zhang
金属学报(英文版)
The influence of pH value of the electrolyte solution on the zinc electroplating process was studied by means of cyclic voltammetry and chronoamperometry approaches. The results shown that, under this experimental conditions and at high overpotentials, the nucleation of zinc is instantaneous, and the nuclear densities N increase with the overpotentials. While at low potentials, no distinguished nucleation current can be observed. High pH promotes the deposition either by drifting the initial depositing potential positively, or by increasing the depositing current through the change of the total charge of the adsorption process Qads, i.e., theｖstructure of electrochemical double layer.
关键词:
zinc electroplating
,
null
,
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