scholarly journals Making Replicas of Surfaces for TEM and SEM

2006 ◽  
Vol 14 (2) ◽  
pp. 50-50
Author(s):  
Mary Mager
Keyword(s):  
Heavy Metal ◽  
Metal Matrix ◽  
Sample Surface ◽  
Original Position ◽  
Second Phase ◽  
Original Surface ◽  
Second Phase Particles ◽  
Carbon Coated ◽  
Coated Surface

Before SEMs were invented and when they were still of relatively poor resolution, one way to see the fine details of a sample surface was to prepare an electron-transparent replica of the sample surface and view it in a TEM. The carbon-coated surface of the sample was shadowed with a heavy metal to make a replica that mimicked the topography of the original surface, in a sample that could be viewed in the TEM.We have found some value in this old technique; to examine second-phase particles freed from the metal matrix for EDX, diffraction, and morphology studies—while preserving the original position and distribution of the particles, historically called “extraction replication.”

The effect of particle height on the analysis of precipitates in alloy foils

1983 ◽  
Vol 41 ◽  
pp. 372-373
Author(s):  
Robert M. Allen
Keyword(s):  
Secondary Electron ◽  
Sample Surface ◽  
Second Phase ◽  
Optimal Position ◽  
X Ray ◽  
Alloy 800 ◽  
Alloy Foil ◽  
Second Phase Particles ◽  
The Matrix ◽  
Electron Image

The relative height of small second-phase particles within a thin alloy foil can have a significant effect on the characteristic x-ray signal obtained from the particle during microanalysis in a STEM. Figure 1 illustrates this for the case where the energy dispersive x-ray detector attached to the STEM views the sample on the side entered by the incident electron beam. If the particle is located below the top foil surface, as in Fig. 1a, beam spreading may reduce the total current striking the particle, thereby reducing the generated signal. The x-ray spectrun of the particle may be further reduced and distorted by matrix absorption en route to the detector. Clearly the optimal position for microanalysis is shown in Fig. 1b: The particle to be analyzed should be on the sample surface facing the beam and x-ray detector.These considerations were demonstrated in an experiment performed on a sample of Alloy 800, a high-allqy austenitic steel. The STEM used was a JEQL 200CX operated at 200kV. The second phase particles (Ti-carbides in this case) in the Alloy 800 electropolished at different rates from the matrix during sample preparation. Those particles located at the surface of the foil after thinning therefore produced surface relief and could be imaged using the secondary electron detector on the STEM. Figure 2 shows a mixed secondary electron/transmitted electron image of the TiC particles analyzed for this experiment.

Structure and chemical composition of nanophase particles in Mg-based alloys

1993 ◽  
Vol 51 ◽  
pp. 990-991
Author(s):  
V. Radmilovic ◽  
G. Thomas
Keyword(s):  
Metal Matrix ◽  
Size Range ◽  
Second Phase ◽  
Particle Size Range ◽  
Typical Structure ◽  
Aerospace Applications ◽  
Transmission Electron ◽  
Second Phase Particles ◽  
Large Particles ◽  
Sic Particulates

Conventional and high resolution transmission electron microscopy, as well as microchemical analyses, are playing an important role in identifying precipitates in Mg based alloys for aerospace applications, especially for nanometer sizes. During aging of Mg-Al-Nd-Zn based alloys, Al-Nd-Zn based particles precipitate which affect the mechanical properties. These alloys, which serve as the metal matrix for MMC materials containing SiC particulates as reinforcement, are processed by rapid solidification/powder metallurgy techniques, and they are designed for relatively high temperature (250-300° C) applications.Figure 1 shows the typical structure of second-phase particles in the Mg-based matrix. The spread in the particle size range is quite large, e.g., roughly between 70 and 100 nm. Close examination of these particles shows (Fig. 2) that there is no coherency with the Mg-based matrix, and no specific crystallographic relationship has been established. In some cases the growing direction of large particles was found to be within 5° of the C-axis of the Mg matrix.

Polishing process effect on the image of dispersed precipitates

1984 ◽  
Vol 42 ◽  
pp. 534-535
Author(s):  
C.T. Hu ◽  
C.W. Allen
Keyword(s):  
Matrix Material ◽  
Specimen Preparation ◽  
Second Phase ◽  
Precipitate Particle ◽  
Polishing Process ◽  
Second Phase Particles ◽  
The Matrix ◽  
Surface Profiles ◽  
Thinning Process

One important problem in determination of precipitate particle size is the effect of preferential thinning during TEM specimen preparation. Figure 1a schematically represents the original polydispersed Ni3Al precipitates in the Ni rich matrix. The three possible type surface profiles of TEM specimens, which result after electrolytic thinning process are illustrated in Figure 1b. c. & d. These various surface profiles could be produced by using different polishing electrolytes and conditions (i.e. temperature and electric current). The matrix-preferential-etching process causes the matrix material to be attacked much more rapidly than the second phase particles. Figure 1b indicated the result. The nonpreferential and precipitate-preferential-etching results are shown in Figures 1c and 1d respectively.

Analytical Electron Microscopy Study of Second-Phase Particles in 7075 and 7475 Aluminum Alloys

1985 ◽  
Vol 43 ◽  
pp. 348-349
Author(s):  
M. Raghavan ◽  
J. Y. Koo ◽  
J. W. Steeds ◽  
B. K. Park
Keyword(s):  
Aluminum Alloys ◽  
Silicon Oxide ◽  
Analytical Electron Microscopy ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Partial Substitution ◽  
Second Phase ◽  
X Ray ◽  
Second Phase Particles ◽  
Almost All

X-ray microanalysis and Convergent Beam Electron Diffraction (CBD) studies were conducted to characterize the second phase particles in two commercial aluminum alloys -- 7075 and 7475. The second phase particles studied were large (approximately 2-5μm) constituent phases and relatively fine ( ∼ 0.05-1μn) dispersoid particles, Figures 1A and B. Based on the crystal structure and chemical composition analyses, the constituent phases found in these alloys were identified to be Al7Cu2Fe, (Al,Cu)6(Fe,Cu), α-Al12Fe3Si, Mg2Si, amorphous silicon oxide and the modified 6Fe compounds, in decreasing order of abundance. The results of quantitative X-ray microanalysis of all the constituent phases are listed in Table I. The data show that, in almost all the phases, partial substitution of alloying elements occurred resulting in small deviations from the published stoichiometric compositions of the binary and ternary compounds.

scholarly journals Evidence of hydrogen trapping at second phase particles in zirconium alloys

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Christopher Jones ◽  
Vidur Tuli ◽  
Zaheen Shah ◽  
Mhairi Gass ◽  
Patrick A. Burr ◽  
...  
Keyword(s):  
Density Functional ◽  
Secondary Ion Mass Spectrometry ◽  
Zirconium Alloys ◽  
Nuclear Industry ◽  
Second Phase ◽  
Hydrogen Trapping ◽  
Functional Theory ◽  
Second Phase Particles ◽  
Hydrogen Isotope Ratios ◽  
Dft Modelling

AbstractZirconium alloys are used in safety–critical roles in the nuclear industry and their degradation due to ingress of hydrogen in service is a concern. In this work experimental evidence, supported by density functional theory modelling, shows that the α-Zr matrix surrounding second phase particles acts as a trapping site for hydrogen, which has not been previously reported in zirconium. This is unaccounted for in current models of hydrogen behaviour in Zr alloys and as such could impact development of these models. Zircaloy-2 and Zircaloy-4 samples were corroded at 350 °C in simulated pressurised water reactor coolant before being isotopically spiked with 2H2O in a second autoclave step. The distribution of 2H, Fe and Cr was characterised using nanoscale secondary ion mass spectrometry (NanoSIMS) and high-resolution energy dispersive X-ray spectroscopy. 2H− was found to be concentrated around second phase particles in the α-Zr lattice with peak hydrogen isotope ratios of 2H/1H = 0.018–0.082. DFT modelling confirms that the hydrogen thermodynamically favours sitting in the surrounding zirconium matrix rather than within the second phase particles. Knowledge of this trapping mechanism will inform the development of current understanding of zirconium alloy degradation through-life.

scholarly journals On the variety and formation sequence of second-phase particles in nickel-based superalloys fabricated by laser powder bed fusion

Materialia ◽  
2021 ◽  
Vol 15 ◽  
pp. 101037
Author(s):  
A. Després ◽  
C. Mayer ◽  
M. Veron ◽  
E.F. Rauch ◽  
M. Bugnet ◽  
...  
Keyword(s):  
Second Phase ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Second Phase Particles

Research of Thermodynamics and Properties of Pb/WC-Zro2 Inert Electrodes Used in Zinc Electrodeposition

2010 ◽  
Vol 136 ◽  
pp. 43-47
Author(s):  
Rui Dong Xu ◽  
Jun Li Wang ◽  
Jian Feng Zhou
Keyword(s):  
Catalytic Activity ◽  
Oxygen Evolution ◽  
Metal Matrix ◽  
Stable Region ◽  
Alloy Electrode ◽  
Second Phase ◽  
Acid Solutions ◽  
Zro2 Particle ◽  
Zinc Electrodeposition ◽  
Inert Electrode

This research is to fabricate a Pb/WC-ZrO2 inert electrode used in zinc electrodeposition. First, the potential-pH diagram of Pb-H2O system was constructed and the thermodynamic stable region was calibrated in the diagram. On the basis, the co-deposition of Pb, WC and ZrO2 particles from fluorboric acid solutions was realized on the surface of Pb-4wt%Sb substrate. The results show that deposition amounts of ZrO2 and WC particles in the inert electrodes increase with increasing ZrO2 concentrations in the bath, WC particle is easier to deposit into the inert electrodes than ZrO2 particle. The distribution of WC and ZrO2 particles as the second phase within metal matrix Pb is very uniform. Compared with Pb-1wt%Ag alloy electrode, Pb/9.91wt%WC-3.62wt%ZrO2 inert electrode possesses better catalytic activity of oxygen evolution.

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