Abstract:Nanocomposites show the best performance when their reinforcing phase precipitates in situ from a matrix upon heat treatment and when coherency between the matrix and the reinforcing phase is preserved even upon coarsening the precipitated particles. In this paper, first a new equation is derived for the interfacial energy of strained coherent interfaces. From here, a new design rule is derived in a form of a new dimensionless number to select phase combinations for in situ coherent nanocomposites (ISCNCs). Th… Show more
“…Note that this critical temperature is probably somewhat reduced due to high specific surface area (not curvature) of the nanoparticles shown in Fig. 9 (see 71 ). Figure 10 Equilibrium phase diagram of the Co-Fe alloy system 63 .…”
Section: Theoretical Partmentioning
confidence: 96%
“…Note: the equilibrium lines will shift down and to the middle by reducing the size, i.e. increasing the specific surface are of the system 71 . …”
An efficient and reproducible growth of vertically aligned carbon nanotubes by CCVD requires accurate and specific setting of the synthesis parameters and the properties of catalyst thin layers. In this work, the growth of vertically aligned carbon nanotubes onto AZO (= aluminum doped zinc oxide) glass substrate covered by Al2O3 and Fe-Co catalyst layer system is presented. Investigation of the effect of catalyst composition and synthesis temperature on CVD growth revealed the optimum condition of the synthesis. The analysis of as-prepared samples by SEM, TEM and Raman spectroscopy was carried out to prove the structure and quality of carbon deposit. Theoretical considerations have supported speculative ideas about the role of the support layer, the transformation of the catalyst layer in the presence of hydrogen gas and the growth mechanism of carbon nanotubes. The mechanism of CNT growth is modelled and the order of magnitude of experimentally observed vertical linear growth rate of CNT (several nm/s) is reproduced.
“…Note that this critical temperature is probably somewhat reduced due to high specific surface area (not curvature) of the nanoparticles shown in Fig. 9 (see 71 ). Figure 10 Equilibrium phase diagram of the Co-Fe alloy system 63 .…”
Section: Theoretical Partmentioning
confidence: 96%
“…Note: the equilibrium lines will shift down and to the middle by reducing the size, i.e. increasing the specific surface are of the system 71 . …”
An efficient and reproducible growth of vertically aligned carbon nanotubes by CCVD requires accurate and specific setting of the synthesis parameters and the properties of catalyst thin layers. In this work, the growth of vertically aligned carbon nanotubes onto AZO (= aluminum doped zinc oxide) glass substrate covered by Al2O3 and Fe-Co catalyst layer system is presented. Investigation of the effect of catalyst composition and synthesis temperature on CVD growth revealed the optimum condition of the synthesis. The analysis of as-prepared samples by SEM, TEM and Raman spectroscopy was carried out to prove the structure and quality of carbon deposit. Theoretical considerations have supported speculative ideas about the role of the support layer, the transformation of the catalyst layer in the presence of hydrogen gas and the growth mechanism of carbon nanotubes. The mechanism of CNT growth is modelled and the order of magnitude of experimentally observed vertical linear growth rate of CNT (several nm/s) is reproduced.
Aluminium (Al) and Al-based alloys known as lightweight, good corrosion resistance, and low-cost materials are found used for a range of engineering applications including those in automobile, aircraft, power systems, marine, defence, and among others. Although, notwithstanding these intrinsic features of Al and its alloys, their wide application is constrained due to certain properties, for example, dendrite separation, intense wear rate over a period, and mechanical degradation under severe impact and harsh environment. Nonetheless, as studies established that nanocomposites depict a promising solution to overcome the limitations of Al, Al-based alloy and their micro composites. The current review aims to discuss the influence of nanoceramic fillers on the mechanical and tribological characteristics of Al and Al alloy-based composites prepared via melting and powder metallurgy routes. With the available literature, the mechanical and wear resistance properties of Al and Al alloys matrix were observed to be improved by different nanoceramic fillers addition. Though, their mechanical behaviour at a certain point undergoes degradation due to particles agglomeration and porosity. Again, issues like brittleness reportedly affect the superior properties’ improvement of Al-based nanocomposites. Thus, as particles agglomeration, porosity, and brittleness are the main drawbacks associated with the development and characterization of Al-based nanocomposites, the authors concluded the study with challenges and recommendations for future improvement. Hence, the study will pave the way for future research opportunities and sustainable development of Al nanocomposites.
The phase rule of Gibbs is one of the basic equations in phase equilibria. Although it has been with us for 150 years, discussions, interpretations and extensions have been published. Here, the following new content is provided: (i). the choice of independent components is discussed, and the component rule is introduced, (ii). independent state variables are divided into compositional and non-compositional ones, (iii). the generalized phase rule is derived replacing number two in the original phase rule by the number of independent non-compositional state variables introduced above, (iv). the degree of freedom is decreased by the number of compositional constraints in special points (azeotrope and congruent melting) of phase diagrams, (v). a rule is derived connecting the maximum number of coexisting phases with the dimensions of the phase diagram, (vi). examples show how to apply the phase rule to unary, binary and ternary phase diagrams and their sections, (vii). the same is extended with the discussion of calculable and not calculable phase fractions, (viii). it is shown that the current definition of the degree of freedom is not sufficient in the number of cases, (ix). the current definition of the degree of freedom is extended, (x). the application of the generalized phase rule is demonstrated when other non-compositional state variables are applied for nano-phase diagrams, and/or for phase diagrams under the influence of electric potential difference, external magnetic field, mechanical strain or the gravitational field.
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