“…The TiB whisker is prone to nucleate along the titanium plane, which has Ti atomic arrangements similar to the (100) TiB plane, such as the (112) β -Ti plane and so on. This can explain why similar orientation relationships have been observed by us and others. − 8 Schematic diagrams of atoms projection of TiB along the (a) [010] TiB and (b) [001] TiB directions. 9 Morphology of deep-etched TiB whiskers having a hexagonal cross section.…”
In situ TiB whisker reinforced Ti-4.0Fe-7.3Mo matrix composites have been fabricated by spark plasma sintering
(SPS). The microstructure of the in situ TiB whiskers and interfacial structures in the composites were investigated by scanning
electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution electron microscopy (HREM). The interfaces
between in situ TiB and the Ti matrix are clean and faceted along the (100)TiB plane. However, small lateral growth steps are
observed along the (101) and (101̄) planes of TiB. Because of the characteristics of the TiB crystal structure, the growing velocity
of the (100)TiB plane along the [010]TiB direction is much faster than that of the [001]TiB direction, which leads to TiB growth as a
whisker shape along the [010]TiB direction with a hexagonal transverse section. The growth mechanism of TiB whiskers is a stacking
process of the (100)TiB plane.
“…The TiB whisker is prone to nucleate along the titanium plane, which has Ti atomic arrangements similar to the (100) TiB plane, such as the (112) β -Ti plane and so on. This can explain why similar orientation relationships have been observed by us and others. − 8 Schematic diagrams of atoms projection of TiB along the (a) [010] TiB and (b) [001] TiB directions. 9 Morphology of deep-etched TiB whiskers having a hexagonal cross section.…”
In situ TiB whisker reinforced Ti-4.0Fe-7.3Mo matrix composites have been fabricated by spark plasma sintering
(SPS). The microstructure of the in situ TiB whiskers and interfacial structures in the composites were investigated by scanning
electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution electron microscopy (HREM). The interfaces
between in situ TiB and the Ti matrix are clean and faceted along the (100)TiB plane. However, small lateral growth steps are
observed along the (101) and (101̄) planes of TiB. Because of the characteristics of the TiB crystal structure, the growing velocity
of the (100)TiB plane along the [010]TiB direction is much faster than that of the [001]TiB direction, which leads to TiB growth as a
whisker shape along the [010]TiB direction with a hexagonal transverse section. The growth mechanism of TiB whiskers is a stacking
process of the (100)TiB plane.
“…The GB structure in NC-materials is still controversial in terms of whether a ''gas-like'' structure can exist in the GBs of NC-materials. Most of the research accomplished to date shows that the GB structure of NC-materials is ordered and is similar to those in coarse-grained materials (Ganapathi and Rigney, 1990;Li et al, 1993;Siegel, 1994;Suryanarayana, 1995). In ball milled copper, the conclusions are similar to those drawn above.…”
HREM and FEG TEM were emphasized and extensively used to follow the most subtle changes in the structure and composition of ball-milled Cu, Fe-Cu, and thermally decomposed Fe60Cu40. Some significant results are obtained and summarized as follows: HREM shows that the deformation of ball-milled copper proceeds mainly by twinning and shear bands (SBs) formation. The nano-grains formed during ball milling (BM) contain a high density of dislocations. The grain boundaries (GBs) of nanocrystalline (NC) Cu prepared by BM are ordered, curved, and strained, but disordering, lattice distortion, and nanovoids in local regions were frequently observed. Nanoscale composition analysis on mechanically alloyed Fe16Cu84 shows that the average Fe content in both the interior of grains and the GBs is close to the designed composition, which proves that a supersaturated solid solution has really formed. However, the Fe content is rather inhomogeneous between the larger and smaller grains, which infers the inhomogeneous mixing of Fe and Cu during mechanical alloying (MA). NC structure and the mechanical force-enhanced fast diffusion are the reasons of the formation of supersaturated solid solutions in immiscible systems with positive enthalpy of mixing. HREM observations carried out with the thermally decomposed Fe60Cu40 solid solution show that the Nishiyama (N-W) or Kurdyumov-Sachs (K-S) orientation relationships exist between alpha-Fe and Cu. Energy dispersive X-ray spectra (EDXS) results show that the Cu content in these alpha-Fe grains reaches as high as 9.5 at.% even after heating to 1,400 degrees C, which is even higher than the maximum solubility of Cu in gamma-Fe at 1,094 degrees C.
“…Incorporation of bi- or tri-component materials can improve insufficient activity possessed by single component materials. Studies have shown that the surface structure of a composite has a strong influence on its stability and catalytic properties. − Transition metal carbides such as WC, TiC, and MoC and their composites are becoming increasing important due to their diverse physical and chemical properties for various applications. − WC materials, in particular, have demonstrated platinum-like surface properties in many surface science and catalysis studies, including those initially investigated by Levy and Boudart and more recently by Bosco …”
Core-shell composites with strong phase-phase contact could provide an incentive for catalytic activity. A simple, yet efficient, HO-mediated method has been developed to synthesize a mesoscopic core-shell W@WC architecture with a dodecahedral microstructure, via a one-pot reaction. The HO plays an important role in the resistance of carbon diffusion, resulting in the formation of the W core and W-terminated WC shell. Density functional theory (DFT) calculations reveal that adding W as core reduced the oxygen adsorption energy and provided the W-terminated WC surface. The W@WC exhibits significant electrocatalytic activities toward hydrogen evolution and nitrobenzene electroreduction reactions, which are comparable to those found for commercial Pt/C, and substantially higher than those found for meso- and nano-WC materials. The experimental results were explained by DFT calculations based on the energy profiles in the hydrogen evolution reactions over WC, W@WC, and Pt model surfaces. The W@WC also shows a high thermal stability and thus may serve as a promising more economical alternative to Pt catalysts in these important energy conversion and environmental protection applications. The current approach can also be extended or adapted to various metals and carbides, allowing for the design and fabrication of a wide range of catalytic and other multifunctional composites.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
