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 solid–liquid interfacial free energy of silicon was calculated by the method based on classical nucleation theory (CNT), where the molecular dynamic (MD) simulations were carried out, and a series of cylindrical solid nuclei were equilibrated with undercooled liquid phase to create an ideal model of a homogeneous nucleation. The interfacial free energy was extracted from the relationship between the critical nuclei radii and their corresponding equilibrium temperatures. The influence of the interfacial curvature on its free energy was for the first time considered in our work, the influence can be measured by a Tolman length which was introduced to modify the traditional CNT; therefore, more accurate results were obtained. The averaged melting point and Tolman length extracted from simulations were 1678.27 K and 2.82 Å, respectively, which are consistent with the expected results. The averaged interfacial free energy is 401.92 mJ/m2, which is in good agreement with the results from experiments.

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.

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.

A series of Ni0.5Zn0.5Fe2O4 (NZO)/polyvinylidene fluoride (PVDF) composites were prepared and studied for their potential application as magneto-dielectric antenna substrate materials. The NZO ferrite powders were synthesized by the solid-state reaction method and then annealed at different temperatures of 700, 900 and 1100 °C. The influence of the annealing treatment on the grain size, crystallinity and magneto-dielectric properties were discussed. The magnetic and dielectric properties of the composites were measured in 1 MHz–1 GHz and 100 Hz–1 GHz, respectively. With the annealing temperature increase from 700 to 1100 °C, the initial permeability of the composites increases from 3.89 to 7.93, while the static permittivity changed regularly with the growing grain size. Almost equal values of μ′ and ε′ are obtained in the composite sample with the 1100 °C annealed NZO powders. Considering the relatively low magnetic and dielectric loss tangent, this material is the promising candidate for the design of miniaturized antennas.

To develop microwave absorbing materials over X and Ku-band, M-type hexaferrites: BaCoxTixFe(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.

Novel nanogranular flakes in which magnetic metallic nanoparticles are highly dispersed in an oxide matrix were fabricated for use as a constituent material in bulk nanogranular composites. A simple milling process using core/shell nanoparticles of magnetic metal/oxide was used to produce nanogranular flakes composed of magnetic metallic nanoparticles in an oxide matrix. The high dispersion of the metallic nanoparticles in the oxide matrix increased the electrical resistivity of the flakes. In addition, neighboring nanoparticles in the flakes interacted with each other via magnetic exchange coupling, and the flakes exhibited good soft magnetism with low coercivity when they contained a high concentration of highly dispersed magnetic metallic nanoparticles. The coercivity of the flakes could be decreased significantly by annealing and by modifying the surface of the flakes. A minimum coercivity of 8.7 Oe was obtained using flakes with a composition of Fe0.5Ni0.5–4 wt% Si.

In this paper, a novel afterglow phosphor based on praseodymium ion doped Sr2Ta2O7 was synthesized successfully by solid-state reaction in the ambient atmosphere. The photoluminescence, afterglow, afterglow decay, and thermoluminescence (TL) properties were investigated in detail. The dependence of photoluminescence properties and long afterglow (LAG) performances on Pr3+ contents were investigated systematically. The optimal concentrations of Pr3+ ions for the best photoluminescence and LAG properties were experimentally to be 2 mol% and 0.5 mol%, respectively. Pr3+ exhibits prominent red emission in most reports, which derives from the 1D2 → 3H4 transition. However, the predominant blue emission locating at ∼489 and ∼507 nm coming from 3P0,1 → 3H4 transitions were observed in praseodymium ion-doped Sr2Ta2O7. Based on TL measurements, the trapping and de-trapping processes of charge carriers between shallower and deep traps were illustrated. A model was proposed on the basis of experimental results to explain the mechanisms of photoluminescence and LAG.

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.

Petroleum coke (PC) is a low-cost and potential carbon source for electrochemical energy storage. To expand the utilization of PC in supercapacitor, PC-based activated carbons (PCACs) with heteroatoms-doped were prepared from PC by KOH chemical activation. The as-prepared carbon exhibited a high surface area (2326.4 m2/g) and hierarchical micro-mesoporous structure, resulting in a high specific capacitance (421 F/g at 1 A/g) and excellent rate performance in KOH electrolyte (217 F/g at 50 A/g). Meanwhile, to improve the high-rate capacitive performance of PCACs in H2SO4 electrolyte, functionalized activated carbon (HQ/PCAC-4) was prepared by physically adsorbing the hydroquinone (HQ) on PCACs. The HQ/PCAC-4 showed an unprecedented capacitance value of 300.2 F/g even at an ultrahigh current density of 50 A/g. In addition, the energy density of HQ/PCAC-4 in H2SO4 electrolyte reached 19.5 W h/kg. The high energy density and excellent rate performance ensured their prosperous application in high-power energy storage system.

The influence of hydrostatic compression on the charge transport properties of an excellent 2,6-diphenylanthracene (2,6-DPA) semiconducting single crystal was investigated up to 10 GPa by performing density-functional calculations together with the tight binding approximation. In this pressure region the lattice constants a, b and c decrease by up to 0.948 Å (5.23%), 1.30 Å (17.26%), and 0.711 Å (11.34%), respectively, while the monoclinic angle β increases by 3.4°. The unit-cell volume decreases by increasing pressure, and the volume decreases by 30.5% at 10 GPa. In comparison, the C–C and C–H intermolecular distances within and between the herringbone layers reduced by 16–19% and 16–24%, respectively, in the same pressure ranges. The results indicate that under high pressure, the molecular planes of the crystal become more and more parallel to each other due to molecular rearrangement in the 2,6-DPA crystal. The band gap decreases with increasing pressure due to decreasing intermolecular separation between neighboring molecules. Finally, the results indicate an improvement of the hole mobility of 2,6-DPA single crystals under hydrostatic pressure.

The new processing method of spark plasma sintering (SPS) followed by hot extrusion was developed to produce Mg–1Al–xCNTs composites. Microstructural characterization revealed that the reinforcement particles were distributed uniformly in Mg matrix. The results of mechanical properties indicated a fact that compared with monolithic Mg, all Mg–1Al–xCNTs composites, especially the Mg–1Al–0.15CNTs composite, fabricated by SPS followed by hot extrusion exhibited better tensile and compressive properties. Under tension, Mg–1Al–0.15CNTs composite exhibited higher 0.2% tensile yield strength (TYS) (157 MPa versus 98 MPa, increased by ∼60%) and ultimate tensile strength (271 MPa versus 188 MPa, increased by ∼44%) than monolithic Mg. In compression, Mg–1Al–0.15CNTs composite also obtained a great enhancement in 0.2% compressive yield strength (118 MPa versus 81 MPa, increased by ∼46%) and ultimate compressive strength (321 MPa versus 255 MPa, increased by ∼26%) compared to monolithic Mg. Meanwhile, Mg–1Al–0.15CNTs composite maintained a high tensile failure strain of ∼8.8% and a high compressive failure strain of ∼17.9%.

By using high purity aluminum powders and multi-walled carbon nanotubes (MWCNTs) as raw materials, MWCNTs/Al composites were fabricated with ball milling, followed by cold pressing, vacuum sintering, and hot extrusion. It was found that when the sintering temperature was 863 K, MWCNTs/Al composite sintered for 4 h showed good comprehensive properties, and its tensile strength and elongation reached to 156 MPa and 21%, respectively. The comprehensive mechanical properties of the composites became better with raising sintering temperature when the sintering time was 4 h. When the sintering temperature raised to 923 K, the tensile strength of the composite reached to 167 MPa which is three times more than that of annealed high purity aluminum, mainly due to the higher density and better interface bonding resulted from higher sintering temperature. CNTs' pulling out were observed obviously in the fractured surfaces, and load transfer may be the main strengthening mechanism.

Four types of W-doped graphite-like carbon (W-GLC) films were deposited under different W target currents by magnetron sputtering method. The effects of W content on the microstructure and properties of the W-GLC films were analyzed via various characterization techniques. The results show that the microstructure of the W-GLC films tends to be loose, while the surface roughness distinctly increases with the increase in the W target current. Moderate W-doping can considerably improve the mechanical properties and wear resistance of the film, which will subsequently decrease as the W content becomes excessive. Moreover, the friction coefficient of the W-GLC films does not show a distinct change, but significantly increases when the W target current increases from 0.9 A to 1.2 A. In particular, when the W target current is 0.6 A, the friction coefficient and the wear rate of the W-GLC film are 0.02 and 3.8 × 10−17 m3/N·m, respectively, exhibiting excellent tribological properties.

Surface roughness and finite sample thickness are major sources of error in the nanoindentation measurements of thin films as the former makes it difficult to determine the effective contact point between the indenter and sample while the latter limits the usable depth range to be no more than ∼10% of the film thickness. Combining a closed-form model of a film/substrate system with the ability of nanoindentation to monitor the contact depth, the present method defines the two-dimensional shape profile of the indenter contacting the composite system with one unknown constant associated with the model and another unknown constant associated with the effective contact point. On the basis that the obtained shape profile of the rigid indenter is identical to the pre-determined indenter shape profile function, the method extrapolates the two constants simultaneously so as to determine the effective contact point. The method was demonstrated for amorphous diamond-like carbon (DLC) coatings.

The fracture toughness of NiAl single crystals is evaluated with a new method based on the J-integral concept. The new technique allows the measurement of continuous crack resistance curves at the microscale by continuously recording the stiffness of the microcantilevers with a nanoindenter. The experimental procedure allows the determination of the fracture toughness directly at the onset of stable crack growth. Experiments were performed on notched microcantilevers which were prepared by focused ion beam milling from NiAl single crystals. Stoichiometric NiAl crystals and NiAl crystals containing 0.14 wt% Fe were investigated in the so-called “hard” orientation. The fracture toughness was evaluated to be 6.4 ± 0.5 MPa m1/2 for the stoichiometric sample and 7.1 ± 0.5 MPa m1/2 for the iron containing sample, indicating that the addition of iron enhances the ductility. This effect is intensified with ongoing crack propagation where the Fe-containing sample exhibits a stronger crack resistance behavior than the stoichiometric NiAl single crystal. These findings are in good agreement with macroscopic fracture toughness measurements, and validate the new micromechanical testing approach.

The gradient cemented carbonitrides with brittle cubic phases containing Ti removed in the surface layers were prepared in this paper. The microstructure, composition distribution, fracture morphology, and transverse rupture strength of these materials were investigated systematically. It is found that the difference between the maximum and the nominal cobalt content augments in the gradient layer, the lattice parameter of (Ti,W)C rises in the bulk inside the gradient border, and the (Ti,W)C cubic phases are refined in the inner bulk as the nitrogen is increased. Besides, the area fraction of WC in the gradient layer is higher than in the bulk, but it decreases remarkably close to the gradient border. The improvement of transverse rupture strength stability depends on thickening of gradient layers, and additionally the transgranular fracture of (Ti, W)C cubic phase can be hardly found in the gradient layer.

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.