In
this work, the role that manganese plays in determining the
structure and performance of sintered biodegradable porous Fe–Mn
alloys is described. Powder metallurgy processing was employed to
produce a series of biodegradable porous Fe-xMn (x = 20, 30, and 35 wt %) alloys suitable for bone scaffold
applications. Increasing manganese content increased the porosity
volume in the sintered alloys and influenced the ensuing properties
of the metal. The Fe-35Mn alloy possessed optimum properties for orthopedic
application. X-ray diffraction analysis and magnetic characterization
confirmed the predominance of the antiferromagnetic austenitic phase
and ensured the magnetic resonance imaging (MRI) compatibility of
this alloy. The porous Fe-35Mn alloy possessed mechanical properties
(tensile strength of 144 MPa, elastic modulus of 53.3 GPa) comparable
to human cortical bone. The alloy exhibited high degradation rates
(0.306 mm year–1) in simulated physiological fluid,
likely due to its considerable Mn content and the high surface area
inherent to its porous structures, while cytotoxicity and morphometry
tests using mammalian preosteoblast cells (MC3T3-E1) indicated good
cell viability in the Fe-35Mn alloy.
Hydrogen has the potential to power much of the modern world with only water as a by-product, but storing hydrogen safely and efficiently in solid form such as magnesium hydride remains a major obstacle. A significant challenge has been the difficulty of proving the hydriding/dehydriding mechanisms and, therefore, the mechanisms have long been the subject of debate. Here we use in situ ultra-high voltage transmission electron microscopy (TEM) to directly verify the mechanisms of the hydride decomposition of bulk MgH2 in Mg-Ni alloys. We find that the hydrogen release mechanism from bulk (2 μm) MgH2 particles is based on the growth of multiple pre-existing Mg crystallites within the MgH2 matrix, present due to the difficulty of fully transforming all Mg during a hydrogenation cycle whereas, in thin samples analogous to nano-powders, dehydriding occurs by a ‘shrinking core' mechanism.
A three-way catalyst (TWC) that concurrently converts three harmful gases, carbon monoxide (CO), hydrocarbons (HCs), and nitrogen oxides (NO x ) is an absolutely essential technique for the sustainable society. Rh has been an essential element in TWC because only Rh is able to efficiently catalytically reduce NO x . [1,2] However, since Rh is scarce metal and its price is very fluctuating, significant efforts have been made to develop alternative TWC catalysts to Rh. Nevertheless, Rh is still irreplaceable, and nowadays, the price of Rh marked an all-time record high.Recently, new alloys of a solid-solution type have been developed as nanoparticles (NPs) and have attracted much attention because some alloys exhibit innovative Since 1970, people have been making every endeavor to reduce toxic emissions from automobiles. After the development of a three-way catalyst (TWC) that concurrently converts three harmful gases, carbon monoxide (CO), hydrocarbons (HCs), and nitrogen oxides (NO x ), Rh became an essential element in automobile technology because only Rh works efficiently for catalytic NO x reduction. However, due to the sharp price spike in 2007, numerous efforts have been made to replace Rh in TWCs. Nevertheless, Rh remains irreplaceable, and now, the price of Rh is increasing significantly again. Here, it is demonstrated that PdRuM ternary solid-solution alloy nanoparticles (NPs) exhibit highly durable and active TWC performance, which will result in a significant reduction in catalyst cost compared to Rh. This work provides insights into the design of highly durable and efficient functional alloy NPs, guiding how to best take advantage of the configurational entropy in addition to the mixing enthalpy.
We report a comprehensive in-situ phase-change study on polycrystalline
Sn0.98Se via high-temperature
X-ray diffraction and in-situ high-voltage
transmission electron microscopy from room temperature to 843 K. The
results clearly demonstrate a continuous phase transition from Pnma to Cmcm starting from 573 to 843 K,
rather than a sudden transition at 800 K. We also find that the thermal-conductivity
rise at high temperature after the phase transition, as commonly seen
in pristine SnSe, does not occur in Sn0.98Se, leading to
a high thermoelectric figure of merit. Density functional theory calculations
reveal the origin to be the suppression of bipolar thermal conduction
in the Cmcm phase of Sn0.98Se due to the
enlarged bandgap. This work fills the gap of in-situ characterization on polycrystalline Sn0.98Se and provides new insights into the outstanding thermoelectric
performance of polycrystalline Sn0.98Se.
the whole area of the SEM micrograph. The resultant data of the five compositions were fitted with linear regression. The fitting and statistical analysis above were performed using SciPy. [55]
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