Microstructural Damage and Evolution of a PbSn Solder Alloy Under Isothermal Cyclic Loading

2002 ◽  
Author(s):  
T. Jesse Lim ◽  
Wei-Yang Lu
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
Solder Alloy ◽  
Room Temperature ◽  
Rich Phase ◽  
Microstructural Damage ◽  
Micro Cracks ◽  
Phase Size ◽  
Pbsn Solder ◽  
Scanning Electron

In our recent experiments, torsional specimens of PbSn Solder Alloy were cyclically loaded under different loading levels at both room temperature and high temperature (1008C). In these experiments, the Pb-rich phase size and micro-crack damage were also observed using scanning electron microscopy in-between loading cycles. At the moderate strain rate (10−4), the growth of Pb-rich phase does not differ much for both temperatures. At room temperature, the damage in the form of micro-cracks along the Pb- and Sn-rich phases are formed during early cycling, and the damage accumulates as the cycling proceeds. At high temperature, the damage does not accumulates as fast as for the similar strain level in room temperature, due to the lowering of stress level in high temperature and dynamic restructuring of Pb-rich phase.

Fretting Wear of T800 Coating in Aero-Engine Applications

2020 ◽  
Author(s):  
Mario Lavella ◽  
Daniele Botto
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
High Temperature ◽  
Dry Friction ◽  
Room Temperature ◽  
Normal Load ◽  
Point Contact ◽  
Dissipated Energy ◽  
Scanning Electron ◽  
Worn Surfaces

Abstract High cycle fatigue in blades is triggered by oscillating forces. Devices such as shrouds, that exploit dry friction, are commonly introduced in the blade assembly to reduce the blade vibrations. If severe wear occurs, the effectiveness of the dry friction damping decreases, vibrations increase, and the number of cycles to failure of the blade diminishes. Mating surfaces in shrouds undergo high loads combined with relative displacement of low amplitude. This is the typical condition known as fretting. Coatings are commonly applied on damping surfaces of turbine blades to mitigate wear. This study investigates the wear mechanism of contact interfaces coated by Tribaloy® T-800, a coating greatly used in aeroengines. The experimental campaign was performed with a point contact test rig. The investigation was carried out using as test parameters temperature, normal load and fretting amplitude. Nine sets of parameters were analyzed at different test durations. Friction coefficients were computed using the hysteresis loops measured during the fretting tests. The worn surfaces were measured by an optical equipment based on focus variation and the volume losses were accurately measured. The wear region was observed by scanning electron microscopy at the end of each test. At room temperature, the friction coefficient was found substantially independent of the normal load. The wear rates at room temperature were higher than at high temperature. Observation of the worn surfaces by scanning electron microscopy revealed several brittle cracks. The damage mechanism changes from brittle (at room temperature) to ductile (at high temperature). The volume loss as a function of the dissipated energy was found independent of the normal load, showing that dissipated energy is a better variable rather than the number of wear cycles to show results of wear tests.

Effect of High Temperature on Morphology and Structure of Nano-Hydroxyapatite/Collagen Composite

2009 ◽  
Vol 610-613 ◽  
pp. 1360-1363 ◽  
Author(s):  
Qiang Song ◽  
Kun Hu ◽  
Fu Zhai Cui ◽  
Zhou Ying He
Keyword(s):  
Electron Microscopy ◽  
Thermal Stability ◽  
Scanning Electron Microscopy ◽  
Fourier Transform ◽  
High Temperature ◽  
Room Temperature ◽  
Energy Dispersive ◽  
X Ray ◽  
Morphology And Structure ◽  
Scanning Electron

Nano-hydroxyapatite/collagen composite was processed at room temperature, 180°C, 200°C and 220°C under atmosphere for 10 min respectively. The morphology of the samples was characterized by scanning electron microscopy (SEM). The structure and components of the samples were investigated by energy dispersive spectrograph (EDS), X-ray powder diffractometer (XRD) and Fourier transform infrared (FTIR). The results of SEM and EDS for nHAC changed greatly at 200°C and 220°C in comparison with room temperature. The morphology and structure of nHAC at 180°C were similar to those at room temperature. It was demonstrated that nHAC possessed thermal stability in morphology and structure.

Scanning Electron Microscopy-cuticular Lesions on the Roundworm Ascaris Suum

1970 ◽  
Vol 28 ◽  
pp. 114-115
Author(s):  
P. A. Madden ◽  
W. R. Anderson
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Freeze Drying ◽  
Room Temperature ◽  
Secondary Electron ◽  
Distilled Water ◽  
Freeze Dried ◽  
Silver Paint ◽  
To Come ◽  
Scanning Electron

The intestinal roundworm of swine is pinkish in color and about the diameter of a lead pencil. Adult worms, taken from parasitized swine, frequently were observed with macroscopic lesions on their cuticule. Those possessing such lesions were rinsed in distilled water, and cylindrical segments of the affected areas were removed. Some of the segments were fixed in buffered formalin before freeze-drying; others were freeze-dried immediately. Initially, specimens were quenched in liquid freon followed by immersion in liquid nitrogen. They were then placed in ampuoles in a freezer at −45C and sublimated by vacuum until dry. After the specimens appeared dry, the freezer was allowed to come to room temperature slowly while the vacuum was maintained. The dried specimens were attached to metal pegs with conductive silver paint and placed in a vacuum evaporator on a rotating tilting stage. They were then coated by evaporating an alloy of 20% palladium and 80% gold to a thickness of approximately 300 A°. The specimens were examined by secondary electron emmission in a scanning electron microscope.

Scanning and Transmission Electron Microscopy of Human Red Blood Cells

1969 ◽  
Vol 27 ◽  
pp. 44-45
Author(s):  
A.J. Tousimis ◽  
T.R. Padden
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Blood Cells ◽  
Room Temperature ◽  
Type Specimen ◽  
New Combination ◽  
Human Red Blood Cells ◽  
Transmission Electron ◽  
Microscope Slides ◽  
Scanning Electron

The size, shape and surface morphology of human erythrocytes (RBC) were examined by scanning electron microscopy (SEM), of the fixed material directly and by transmission electron microscopy (TEM) of surface replicas to compare the relative merits of these two observational procedures for this type specimen.A sample of human blood was fixed in glutaraldehyde and washed in distilled water by centrifugation. The washed RBC's were spread on freshly cleaved mica and on aluminum coated microscope slides and then air dried at room temperature. The SEM specimens were rotary coated with 150Å of 60:40- gold:palladium alloy in a vacuum evaporator using a new combination spinning and tilting device. The TEM specimens were preshadowed with platinum and then rotary coated with carbon in the same device. After stripping the RBC-Pt-C composite film, the RBC's were dissolved in 2.5N HNO3 followed by 0.2N NaOH leaving the preshadowed surface replicas showing positive topography.

Scanning Microscopy of Human Intestinal Explants in Organ Culture

1972 ◽  
Vol 30 ◽  
pp. 396-397
Author(s):  
Bruce Wetzel ◽  
Robert Buscho ◽  
Raphael Dolin
Keyword(s):  
Electron Microscopy ◽  
Room Temperature ◽  
Culture Conditions ◽  
Human Fetuses ◽  
Enteric Disease ◽  
Organ Cultures ◽  
Growth Of A Variety ◽  
Normal Human ◽  
Fetal Intestine ◽  
Scanning Electron

It has been reported that explants of human fetal intestine can be maintained in culture for up to 21 days in a viable condition and that these organ cultures support the growth of a variety of known viral agents responsible for enteric disease. Scanning electron microscopy (SEM) has been undertaken on several series of these explants to determine their appearance under routine culture conditions.Fresh specimens of jejunum obtained from normal human fetuses were washed, dissected into l-4mm pieces, and cultured in modified Leibowitz L-15 medium at 34° C as previously described. Serial specimens were fixed each day in 3% glutaraldehyde for 90 minutes at room temperature, rinsed, dehydrated, and dried by the CO2 critical point method in a Denton DCP-1 device. Specimens were attached to aluminum stubs with 3M transfer tape No. 465, and one sample on each stub was carefully rolled along the adhesive such that villi were broken off to expose their interiors.

SEM Observations on the Germination of Euonymous Americanus

1985 ◽  
Vol 43 ◽  
pp. 508-509
Author(s):  
D.R. Hill ◽  
J.R. McCurry ◽  
L.P. Elliott ◽  
G. Howard
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Light Microscopy ◽  
Filter Paper ◽  
Room Temperature ◽  
Food Source ◽  
Environmental Chamber ◽  
Dormant Stage ◽  
Scanning Electron

Germination of Euonymous americanus in the laboratory has previously been unsuccessful. Ability to germinate Euonymous americanus. commonly known as the american strawberry bush, is important in that it represents a valuable food source for the white-tailed deer. Utilizing the knowledge that its seeds spend a period of time in the rumin fluid of deer during their dormant stage, we were successful in initiating germination. After a three month drying period, the seeds were placed in 25 ml of buffered rumin fluid, pH 8 at 40°C for 48 hrs anaerobically. They were then allowed to dry at room temperature for 24 hrs, placed on moistened filter paper and enclosed within an environmental chamber. Approximately four weeks later germination was detected and verified by scanning electron microscopy; light microscopy provided inadequate resolution. An important point to note in this procedure is that scarification, which was thought to be vital for germination, proved to be unnecessary for successful germination to occur. It is believed that germination was propagated by the secretion of enzymes or prescence of acids produced by microorganisms found in the rumin fluid since sterilized rumin failed to bring about germination.

ROOM TEMPERATURE PHOTOLUMINESCENCE OF POLYCRYSTALLINE SIC PREPARED FROM CARBON-SATURATED SI MELT

2002 ◽  
Vol 16 (06n07) ◽  
pp. 1047-1051
Author(s):  
JIANPING MA ◽  
ZHIMING CHEN ◽  
GANG LU ◽  
MINGBIN YU ◽  
LIANMAO HANG ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
Room Temperature ◽  
Uv Light ◽  
X Ray Diffraction ◽  
X Ray ◽  
Room Temperature Photoluminescence ◽  
Composition And Structure ◽  
Light Excitation ◽  
Scanning Electron

Intense photoluminescence (PL) has been observed at room temperature from the polycrystalline SiC samples prepared from carbon-saturated Si melt at a temperature ranging from 1500 to 1650°C. Composition and structure of the samples have been confirmed by means of X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy. PL measurements with 325 nm UV light excitation revealed that the room temperature PL spectrum of the samples consists of 3 luminescent bands, the peak energies of which are 2.38 eV, 2.77 eV and 3.06 eV, respectively. The 2.38 eV band is much stronger than the others. It is suggested that some extrinsic PL mechanisms associated with defect or interface states would be responsible to the intensive PL observed at room temperature.

Relative Reactivity Trends OP High Temperature Superconductor Phases

1992 ◽  
Vol 275 ◽  
Author(s):  
David R. Riley ◽  
Ji-Ping Zhou ◽  
A. Manthiram ◽  
John T. McDevitt
Keyword(s):  
Electron Microscopy ◽  
Carbon Dioxide ◽  
High Temperature ◽  
High Temperature Superconductor ◽  
Relative Reactivity ◽  
Complete Understanding ◽  
High Tc ◽  
X Ray ◽  
The Common ◽  
Scanning Electron

ABSTRACTMany of the high temperature superconductor phases degrade rapidly when in the presence of water, acids, carbon dioxide or carbon monoxide. In order to foster more rapid developments in the area of high-Tc research, it will be necessary to acquire a more complete understanding of the surface chemistry of these superconducting materials. In this paper, the relative reactivity of the common cuprate phases toward water is reported. X-ray powder diffraction and scanning electron microscopy measurements are utilized here to establish the reactivity trends.

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