The TiO2 hollow spheres (TiO2HS) were successfully prepared by a hydrothermal method and added to Vulcan XC-72 carbon black as the support materials for Pd nanoparticles. A facile approach to promote ethylene glycol (EG) electrooxidation in alkaline medium was carried out by the PdBi/TiO2HS-C catalyst. The results show that Pd and Bi nanoparticles are uniformly dispersed on the surface of carbon-doped TiO2 hollow spheres, the appropriate amount of Bi modification into Pd/TiO2HS-C catalyst can enhance remarkably the electrocatalytic activity for EG oxidation, in which the PdBi/TiO2HS-C (Pd:Bi = 1:0.1) catalyst exhibits excellent stability. The high electrochemical performance is attributed to the unique structure and high surface area of the TiO2HS, metal nanoparticles uniform distribution, the electronic effect between Pd and Bi as well as the bifunctional effect between metal nanoparticles and the support TiO2HS-C. The results obtained are significant for the development of new Pd-based TiO2HS-C electrocatalysts for alcohol fuel cells.

Graphene nanoribbons as a quasi-one-dimensional form of graphene has attracted intensive attention in energy related devices. Upon oxidation and cutting of multiwall carbon nanotubes (MWCNTs), highly dispersive graphene oxide nanoribbons (GONRs) were obtained, on which Zn2+ and Sn4+ can be homogenously deposited. The reduced graphene oxide nanoribbons (rGONRs)/Zn2SnO4 composite with a homogeneous distribution of nanoparticles on the nanoribbons have been prepared through facile in situ chemical co-reduction process. It is worth noting that the size of Zn2SnO4 particles tightly dispersed on rGONRs is about 15 nm. Benefit from the introduction of rGONRs, the specific surface area and electrode conductivity of rGONRs/Zn2SnO4 can both be effectively enhanced. The as-prepared rGONRs/Zn2SnO4 as anode material for lithium-ion batteries displays desirable electrochemical performance (727.2 mA h/g after 50 cycles at the current density of 100 mA/g), which is mainly attributed to the uniformly distributed Zn2SnO4 nanoparticles and the immobilizing and conducting effects of rGONRs.

Silicon emerged as an important substrate material for photonics because of its transparency in the near infrared and its superior planar waveguide properties. Active optoelectronic devices in the infrared wave length regime need semiconductor heterostructures with smaller band gaps as silicon, preferably from the group IV material system. This paper describes fundamental properties of lattice mismatched group IV heterostructures on silicon and their synthesis with epitaxy methods. Special emphasis is given to the aspects of strain management in lattice mismatched device structures and to the realization of metastable non-equilibrium materials. Well-defined strain status is obtained by growth on virtual substrates which consist of silicon substrates with strain relaxed silicon germanium buffer layers. Epitaxy methods at low growth temperatures pushed the synthesis of germanium tin alloys with tin concentrations more than ten times the equilibrium value of about 1%. These achievements pave the way for silicon photonics to efficient light emission and mid infrared operation.

The effects of different Sn contents on the microstructure and tensile properties of an in situ prepared Al–15% Mg2Si composite were investigated. Adding 5 wt% Sn not only reduced the average size of Mg2Si primary particles from ∼55 µm to ∼10 µm, but also increased the ultimate tensile strength and elongation values. Mg2Sn intermetallic was identified in Al–15% Mg2Si–5% Sn composite and the lowest disregistry was also found for $\left( {001} \right)_{{\rm{Mg}}_2 {\rm{Sn}}} {\parallel} \left( {001} \right)_{{\rm{Mg}}_{\rm{2}} {\rm{Si}}}$ , indicating that Mg2Sn can be a potent heterogeneous nucleation site for Mg2Si particles. Computer-aided cooling curve analysis revealed that Sn addition changes the solidification performance of the material by increasing both solidification time and recalescence undercooling and also reducing the growth temperature to some extent. The solidification behavior of the composite was also explained in terms of the presence of oxide bifilms in the liquid Al.

To develop microwave absorbing materials over X and Ku-band, M-type hexaferrites: BaCox Tix Fe(12−2x)O19, with x varying from 0.0 to 1.0 in step size of 0.2, were prepared by solid state reaction route. Characterization techniques like x-ray diffraction, scanning electron micrograph and vibration sample magnetometer were used to analyze the crystalline phases, morphologies, and magnetic properties of the samples. Vector network analyzer was utilized to scrutinize the electromagnetic properties like complex permittivity, complex permeability, and microwave absorption. Results indicate the enhancement of imaginary permittivity and permeability with substitution. Absorption analysis concludes that the composition with x = 0.8 is the best single-layer microwave absorber out of all the prepared compositions with minimum reflection loss −33 dB at thickness of 3.1 mm. At the same time, the compositions x = 0.2, 0.4, 0.6, and 1.0 are combined to form double-layer absorber with absorption more than 99% in X and Ku-band.

Semisolid forging is a type of semisolid metal processing with high solid fraction. However, the presence of nanosized particles has strong influences on flow behavior of the composites in the semisolid forging process. In this study, the compression deformation behavior of nanosized Al2O3 particles (Al2O3np) reinforced 7075 aluminum matrix composites with high solid fraction was investigated by conducting semisolid isothermal compression experiment. The microstructures after semisolid compression were characterized. The results showed that the true stress decreased with the increase of the deformation temperature and size of Al2O3np, the decrease of the strain rate and mass fraction of Al2O3np. After semisolid compression, deformation degree in large deformation zone was larger than that in free deformation zone. Besides, the solid grains in large deformation zone showed evidence of having undergone different degrees of plastic deformation under different deformation conditions. Simultaneously, the deformation mechanisms during the semisolid compression process were discussed.

Beta-gallium oxide (β-Ga2O3) is of increasing interest to the optoelectronic community for transparent conductor and power electronic applications. Considerable variability exists in the literature on the growth and doping of Ga2O3 films, especially as a function of growth approach, temperature, and oxygen partial pressure. Here pulsed laser deposition (PLD) was used to grow high-quality β-Ga2O3 films on (0001) sapphire and (−201) Ga2O3 single crystals and to explore the growth, stability, and dopability of these films as function of temperature and oxygen partial pressure. There is a strong temperature dependence to the phase formation, morphology, and electronic properties of β-Ga2O3 from 350 to 550 °C.

The fatigue crack growth (FCG) tests were performed on a Ni–17Mo–7Cr base superalloy before and after thermal exposure to investigate the influence of microstructural variation on the alloy's FCG behavior. It was observed that the original alloy consists of Ni matrix and MoC particles. When the alloy was aged at 1350 °C for 0.5 h, the MoC melts together with circumambient Ni matrix, forming a eutectic–like structure. The microstructural analysis shows that, for original alloy, the crack basically propagates in the matrix. When it encounters the particles, the crack meanders to avoid them, creating a linear da/dN–ΔK curve. As the crack approaches the eutectic-like structures within the aged alloy, however, it cuts through them but circumvents tiny particles within the structures, producing torturous crack paths and waved da/dN–ΔK curve. The aged alloy has a higher FCG resistance in contrast to original alloy.

Microstructures of new heat-resistant steel grade T23 welded joint without PWHT and its corresponding mechanical properties including creep were investigated to clarify its premature failure mechanisms in the large water wall panel of the advanced power plant boiler. The results show that the T23 steel GTAW welded joint in a wall thickness of 6.5 mm without PWHT exhibits high tensile strength, good ductility, and sufficient impact toughness, while the hardness of the WM is higher than the maximum permitted value of 350 HV due to the large amount of un-tempered martensite formed during the cooling process of welding. This WM in as-welded condition has higher creep rupture strength but poorer rupture ductility than the tempered BM. Poor rupture ductility taken place in the WM results from inter-granular cracking during creep exposure and is not related to the second hardening because no hardness rise occurs in the fractured WM compared with as-welded condition. The paper does not specifically investigate the effect of service exposure but simulates the failure of WM by a creep test. The main point is that the WM has low creep ductility, especially at a stress concentration.

The synergistic effects of the template [Pluronic-123 (P123)] and the silica source [tetraethoxysilane (TEOS)] concentrations on the SBA-15 mesoporous silica morphology were investigated through adjusting the system initial solution volume with the same amounts of silica source and template. It found interestingly that the SBA-15 morphology changed from the hexagonal plate-like shape to the gear-like shape with the decrease of the P123 and TEOS concentration. Based on the morphology variations, the growth of the gear-like morphology was speculated to be formed through the preferential growth at the corner and the layer-by-layer growth in the end face of the ordinary hexagonal plate-like particle.

As-annealed commercial pure titanium (grade 1) was selected as a model material whose crystalline structure was hexagonal close-packed. The evolution of the microstructure and micro-orientation induced by high-speed compression was characterized to elaborate the formation mechanism of the high-speed deformation characteristic microstructure in α-titanium. Twinning played a coordinating role for dislocation slipping that was the main plastic deformation mechanism. The high-speed deformation characteristic microstructure of as-annealed commercial pure titanium was an adiabatic shear band (ASB) with an average width of 50 μm at a strain rate of 5400 s−1, whose initial grains were 0.5–1.0 μm in size. The formation and extension of ASB were attributed to the interaction between the shear stress and the adiabatic temperature rise. A formation model of ASB in α-Ti was proposed in terms of the formation mechanism of the high-speed deformation characteristic microstructure.

Inhomogeneity may lead to premature failure and operationally determines the lifetime estimation of thick weld joints. Considerable novelty of this paper was the achievement of the microstructural and mechanical inhomogeneity, especially along the thickness direction, in the narrow-gap weld seam of thick gas metal arc (GMA) welded Al–Zn–Mg alloy plates. The microstructure of the weld seam was investigated by means of optical metallography, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive spectrum (EDS), after which the phase composition was ascertained according to the x-ray diffraction (XRD) analysis and selected area diffraction analysis by TEM (TEM-SAD). The generation of intergranular short rod-shaped MgZn2 particles changed the distribution of precipitates on the grain boundary with intragranular ellipsoidal MgZn2 particles simultaneously formed as the strengthening phase, which rendered preferable mechanical performances to the bottom layer of the weld seam. The above conclusion was farther affirmed by micro fractography and EDS test results on the fractured surface of the tensile samples. In addition, the effect of following weld passes on the microstructure and micro hardness profile of the finished weld pass was investigated.

The ground state properties of Fe3−x Crx O4 (x = 0–3) compounds were studied using first principles calculation. Stress–strain methods were used to evaluate elastic constants of these compounds. These compounds are mechanically stable structures, because they satisfy the mechanical stability criteria. The mechanical moduli were estimated using the Voigt–Reuss–Hill approximation. The calculated bulk moduli of Fe3O4, Fe2CrO4, FeCr2O4, and Cr3O4 are 190.9 GPa, 135.5 GPa, 180.1 GPa, and 235.6 GPa, respectively. Both of anisotropic indexes and 3-D surface contour were used to illustrate the elastic anisotropy. Debye temperature and anisotropy of acoustic velocity of Fe3−x Crx O4 compounds were also investigated. The maximum Debye temperature is attributing to Cr3O4 with 507.6 K among Fe3−x Crx O4 compounds. The minimum thermal conductivity of Fe3−x Crx O4 compounds was estimated by both Clarke's model and Cahill's model. Moreover, 3-D surface contour of the anisotropic thermal conductivity of Fe3−x Crx O4 compounds was obtained based on the Clarke's model and anisotropic Young's modulus.

The objective of this investigation was to utilize the first-principles molecular dynamics computational approach to investigate the lithiation characteristics of empty silicon clathrates (Si46) for applications as potential anode materials in lithium-ion batteries. The energy of formation, volume expansion, and theoretical capacity were computed for empty silicon clathrates as a function of Li. The theoretical results were compared against experimental data of long-term cyclic tests performed on half-cells using electrodes fabricated from Si46 prepared using a Hofmann-type elimination–oxidation reaction. The comparison revealed that the theoretically predicted capacity (of 791.6 mAh/g) agreed with experimental data (809 mAh/g) that occurred after insertion of 48 Li atoms. The calculations showed that overlithiation beyond 66 Li atoms can cause large volume expansion with a volume strain as high as 120%, which may correlate to experimental observations of decreasing capacities from the maximum at 1030 mAh/g to 553 mA h/g during long-term cycling tests. The finding suggests that overlithiation beyond 66 Li atoms may have caused damage to the cage structure and led to lower reversible capacities.