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M. BAHGAT M.H. KHEDR M.I. NASR E.K. SEDEEK 《Metallurgical and Materials Transactions B》2007,38(1):5-11
Pure nanocrystalline hematite (40 to 100 nm) compacts were prepared and sintered at various temperatures (300 °C to 600 °C)
and then reduced with 100 pct H2 at 500 °C. On the other hand, fired compacts at 500 °C were reduced with a H2-Ar gas mixture containing different concentration of hydrogen (100, 75, 50, and 25 pct) at 500 °C using thermogravimetric
techniques. Nanocrystalline Fe2O3 compacts were characterized before and after reduction with X-ray diffraction, scanning electron microscopy (SEM), vibrating
sample magnetometer (VSM), and reflected light microscope. It was found that the fired compacts at 400 °C to 600 °C have relatively
faster reaction behaviors compared to that at lower firing temperature 300 °C. By decreasing the firing temperature to 300 °C,
partial sintering with grain growth was observed clearly during reduction. Also, it was found that the reduction rate increased
with increasing hydrogen content in the reducing gas. Comparatively, grain growth and partial coalescence took place during
reduction with 25 pct H2 due to long reaction time.
相似文献
M. BAHGAT (Researcher)Email: |
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Joo Hyun Park Sang-Beom Lee Henri R. Gaye 《Metallurgical and Materials Transactions B》2008,39(6):853-861
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Joo Hyun Park 《Metallurgical and Materials Transactions B》2007,38(4):657-663
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Duk-Hyun Nam Kyuhong Lee Sunghak Lee 《Metallurgical and Materials Transactions A》2007,38(6):1193-1201
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P. Wesseling B.C. Ko L.O. Vatamanu G.J. Shiflet J.J. Lewandowski 《Metallurgical and Materials Transactions A》2008,39(8):1935-1941
Annealing studies at different temperatures, as well as those conducted with 940 MPa hydrostatic pressure, were conducted
on amorphous ribbons of Al87Ni7Gd6. The studies were performed to investigate the evolution of structure under different conditions and to particularly examine
the effects of superimposed hydrostatic pressure during annealing. This amorphous alloy devitrifies at low temperatures via the precipitation of nano-crystalline α-Al particles. The effects of these various exposures on the amount of devitrification have been quantified using a variety
of analytical techniques (i.e., X-ray diffraction (XRD), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM)). In addition,
the effects of devitrification on the mechanical properties have been quantified using microhardness indentation and uniaxial
tension tests.
This article is based on a presentation given in the symposium entitled “Bulk Metallic Glasses IV,” which occurred February
25–March 1, 2007 during the TMS Annual Meeting in Orlando, Florida under the auspices of the TMS/ASM Mechanical Behavior of
Materials Committee.
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J.J. Lewandowski (Leonard Case, Jr., Professor of Engineering)Email: |
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