The interface and interfacial reactions in Al-matrix composites reinforced with multi-walled carbon nanotubes (MWCNTs) were thoroughly investigated by high-resolution transmission electron microscopy ...combined with a precisely controlled heat treatment in the solid state. It was shown that MWCNT (002) formed a coherent interface with the low-index Al planes of Al (111), Al (220), and Al (002), realizing a stable interface. Aluminum carbides (Al4C3) were preferentially formed at the active prism plane edges sited at the open ends and acid treatment-induced surface nanodefects of MWCNTs. The Al4C3 maintained the shape of the pristine MWCNT and showed a typical orientation relationship with the Al matrix, that is, Al (111)//Al4C3 (001). It was suggested that the diffusion of Al atoms through Al4C3 dominated the growth of Al4C3; the Al4C3 originated at the open MWCNT tips may quickly grow in the direction of the MWCNT, while the nanodefect-originated Al4C3 may grow simultaneously in the and directions of the MWCNT. The activation energy of Al4C3 formation, the appearance of twinning in single-crystal Al4C3, and the possible influence of the Al4C3 formation on the enhancement of load transfer at the MWCNT/Al interface were also studied.
Aluminum (Al)/carbon nanotube (CNT) composites with nanoscale dispersion and regular orientation of the CNTs were fabricated by a combination of some advanced powder processes. The CNTs were well ...dispersed onto the Al particles by a nanoscale dispersion method. Moreover, the highly densified CNT composites were prepared by spark plasma sintering and subsequent hot extrusion. Microstructural observations by optical, field-emission scanning electron, and high-resolution transmission electron microscopies confirmed that the sintered Al/CNT compact and extruded bulk material had a good dispersion of oriented CNTs. Raman spectroscopy showed that the processing did little damage to the CNTs. As a result, the composites exhibited tensile strengths that were thrice larger than pure aluminum because of the CNT reinforcement.
Lithium diffusion is a key factor in determining the charge/discharge rate of Li-ion batteries. Herein, we study the tracer diffusion coefficient (D*) of lithium ions in the c-axis oriented LiCoO2 ...thin film using secondary ion mass spectrometry (SIMS). We applied a step-isotope-exchange method to determine D* in the Li-extracted LixCoO2. The observed values of D* ranged from 2 × 10−12 to 3 × 10−17 cm2 s−1 depending on the compositions in the range of 0.4 < x < 1.0. Approaching the stoichiometric composition (x = 1.0), D* decreases steeply to the minimum, which can be explained by the vacancy diffusion mechanism. Electrochemically determined diffusion coefficients corrected by thermodynamic factors are found to be in good agreement with D* determined by our method, over a wide range of compositions. The c-axis diffusion was explained by the migration of Li+ ions from one layer to another through additional diffusion channels, such as antiphase boundaries and a pair of Li antisite and oxygen vacancies in cobalt oxide layers.
Fe-based amorphous powder cores of Fe–Si–B–Cr–C magnetic powder and phenolic binder were fabricated, and the effects of annealing and compaction pressure on the soft magnetic properties and core loss ...were investigated. The formation of Fe–B and α-Fe (Si) phases was confirmed at the annealing temperature above 773 K. The density gradually increased from 5.3 to 5.5 g/cm3 as annealing temperature increased, resulting in the saturation magnetization 4πMs increased to 1.0 T at 773 K. The effect of compaction pressure was studied by using samples annealed at 723 K. Both the density and 4πMs enhanced with compaction pressure from 980 to 1960 MPa. The real part of permeability µ’ remained constant for the frequency up to 2 MHz. The initial value of µ’ increased from 25 to 38 with compaction pressure. Consequently, at Bm of 50 mT and frequency of 100 kHz, the considerably low core loss of 67 kW/m3 was obtained. The low core loss and moderately high permeability of Fe–Si–B–Cr–C amorphous powder core across a wide frequency range indicate its potential for application in high frequency electronic components.
The effects of Ga composition (x) on soft and high-frequency magnetic properties of 10-nm-thick B-doped Fe–Ga (Fe85.1−xGaxB14.9) thin films were investigated. A uniaxial magnetic anisotropy appeared ...regardless of the Ga composition. The damping constant values and magnetic inhomogeneous broadening at a zero frequency were much lower than those of the Fe–Ga polycrystalline film for all Ga compositions. These results indicate that adding B atoms to Fe–Ga thin films improves the soft and high-frequency magnetic properties of these films and suggest that Fe–Ga–B thin films are candidate magnetostrictive materials for high-frequency devices.
Tubular shape aluminum (Al) 6063/Al-3 vol% carbon nanotubes (CNT)/Al3003 functionally graded materials (FGMs) were fabricated by hot extrusion process. FGMs is consisted by Al6063 which exhibits high ...strength and hardness, Al-3 vol% CNT which exhibit superior mechanical and thermal properties and Al3003 which has high ductility. The Al-3 vol%CNT powder, which is middle layer of FGMs, was used to increase contact surface area with other materials resulting in improved interface properties. The composite powder was observed using a field-emission scanning electron microscope (FE-SEM). To analyze the microstructures, FGMs were analyzed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and transmission electron microscopy(TEM). Al-3 vol%CNT was recrystallized by friction with bulk. In this zone, the Vickers hardness value was almost 120 HV, which is twice of the values of Al6063and Al3003. Although the FGMs has high strength of 142 MPa, it also realizes high elongation of 22%. We considered some possible strengthening mechanisms, including CNT strengthening, grain refinement, precipitation hardening, and oxide dispersion strengthening.
Abstract
A large relative surface area is crucial for high catalytic activity. Monolithic catalysts are important catalytic materials because of minimal self-degradation. Regarding large surface area ...catalysts, the glass–ceramics (GCs) with high formability, obtained by heat-treatment of the precursor glass, are plausible candidates. This study examines the photocatalytic behaviour of porous GCs obtained after acid leaching of MgO–TiO
2
–P
2
O
5
GCs. After heat-treatment, anatase TiO
2
was precipitated along with other phases. The diffraction intensity ratio between anatase and other phases was the maximum for a heat-treatment temperature of 900 °C. After acid leaching of the GCs, the relative surface area decreased with increasing TiO
2
fraction; the surface area was also affected by the sample morphology. H
2
generation was observed from porous GCs, while GCs without etching exhibited approximately zero activity. Thus, it was demonstrated that high surface area and prevention of the reduction reaction to Ti(III) are important for tailoring monolithic photocatalytic materials.
The microstructure of graphite flake (GF) reinforced aluminum (Al) matrix (Al–GF) composites was observed in detail. Due to thermal mismatch between Al and GF, an inner structure of GF was damaged in ...proximity to the Al/GF interface, while the unique bridging of the sticky graphite sheets barely connected the Al matrix and GF. This result suggests that the GF interlaminar strength is weaker than the Al/GF interfacial strength; the GF interlaminar strength is thus the dominant determinant of the thermomechanical and mechanical properties of the Al–GF composite. Whereas the thermal conductivity of the Al–GF composite was consistent with that theoretically predicted, the outstanding thermal expansion coefficient (TEC) of the graphite was not reflected in the produced Al–GF composites. The damaged inner structure of GF in proximity to the Al/GF interface contributes to heat transfer but does not bear the load resulting from thermal stress.
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