Vertically aligned graphene was grown by plasma-enhanced chemical vapor deposition using methane feedstock. Optical emission spectroscopy (OES) was used to monitor the plasma species, and Raman spectroscopy was used for characterizing the properties of as-grown vertically aligned graphene. OES-derived information on plasma species, such as C, C2, CH, and H, are correlated with the properties of the vertically aligned graphene. Graphene grown at 250 W and 15 sccm exhibited the lowest amount of defects. Although OES peak intensities occurred at the highest power and lowest flow conditions, the OES peak ratios of plasma species had a greater dependence on flow rate and exhibited a saddle point in the atomic C/H ratio corresponding to optimal growth involving the lowest amount of overall defects. Plasma diagnostics provides a valuable approach to optimize growth characteristics and material properties.

Novel europium- and gadolinium-doped bismuth phosphate (Eu/BiPO4 and Gd/BiPO4) microcrystals have been synthesized by a hydrothermal route. The morphologies and optical properties of the as-prepared samples were characterized carefully. Their photocatalytic activities were determined by oxidative decomposition of methylene blue (MB) in aqueous solution. The results revealed that europium and gadolinium doping greatly improves the photocatalytic efficiency of BiPO4 microcrystals. Among these as-prepared europium and gadolinium dopant samples, 1% Eu/BiPO4 and 5% Gd/BiPO4 displayed the highest photocatalytic activity, and the degradation rates are 2 and 2.7 times greater than pure BiPO4, respectively. The photodegradation reactions of MB by Eu- and Gd-BiPO4 followed first-order kinetics. The different photocatalytic mechanisms of Eu/BiPO4 and Gd/BiPO4 photocatalysts are discussed.

Lead-free positive temperature coefficient of resistance (PTC) thermistors were synthesized from (1 − x/100)BaTiO3–(x/100)(Bi1/2K1/2)TiO3-based solid solutions, using a conventional mixed-oxide fabrication route, and sintered in N2 followed by air annealing. A maximum TC of 205 °C was achieved for x = 20. An increase in x from 0 to 20 decreased the grain size by more than 92% and increased room temperature resistivity (ρRT) by 7 orders of magnitude. For x ≤ 10, PTC ratio (ρmax/ρmin) ≈ 104.5 and temperature coefficient of resistivity (α) > 10.3%/°C were achieved using Mn and Al2O3:SiO2:TiO2 (AST) additions. For x > 10, ρmax/ρmin > 103 and α > 8%/°C were only obtained in samples sintered in N2 without subsequent air annealing. Complex impedance analysis revealed three relaxation processes, attributed to a semiconducting grain core, a PTC active grain boundary interface, and a grain boundary insulating layer. Local electrical activity was investigated by hot-stage conductive mode microscopy. The existence of symmetrical grain boundary electron beam-induced current and β-conductivity contrast at the grain boundaries, consistent with the presence of an electron trapping two-dimensional grain boundary plane, compensated by positive space charge layers and a low conductivity vacancy-rich layer, was revealed for the first time within this system.

The present work demonstrates an isothermal reversible variation of magnetization in nanoporous Pd67Ni33 alloy during continuous charging and discharging of the alloy electrode in 1-M KOH solution. A custom-built electrochemical cell, containing the sample as working electrode performed the in situ charging experiments inside an extraction magnetometer at a constant applied magnetic field. The metal–electrolyte response was examined by varying the electrode potential, which apart from polarizing nanoporous structure, may also lead to electrodissociation of the electrolyte medium, being aqueous in nature. The result therefore analyzed hydrogenation as the key parameter for the observed reversible magnetization in the transition metal alloy at room temperature. In addition, electrochemical reactivity due to surface oxidation at the positive potential has been discussed, considering that a change in the band structure is also possible at the negative potential regime due to hydrogenation through cyclic voltammetry study.

Suction casting (SC) and centrifugal casting (CC) are two common special casting processes. The influences of SC and CC on the microstructural development of Cu–10Al–4Fe–4Ni aluminum bronzes were investigated with continuous cooling method. The results indicate that α, β′, KII, and KIII phases are observed in the quasicast microstructure via the SC process with the precipitation sequence of KII → α → KIII. Additionally, KI and KIV are observed in the quasicast microstructure via the CC process with the precipitation sequence of α + KⅠ → KII → KIV → KIII. Phase initial precipitation temperatures of the CC process are higher than that of the SC process, especially for α phase. As the quenching temperature decreases, the hardness of both alloys shows a rapid decline trend and finally reaches a steady state. It is found that the eutectoid decomposition (β → α + KIII) barely affects the hardness of the alloys.

Decoupled growth often occurs in the nonfacetted–facetted eutectic systems. And it is generally considered that the nonfacetted solid solution acts as the leading phase in the decoupled growth. In this work, Fe40Ni40P14B6 eutectic alloys were systematically studied via solidification of undercooled melts and crystallization of amorphous alloys. Upon solidification of melts subjected to different undercoolings, as the undercooling increases, the growth mechanism develops from cooperative growth to decoupled growth. Upon crystallization of amorphous alloys, the partially crystallized sample consists only of strongly faulted intermetallic (Fe,Ni)3(P,B) with chemical composition deviating from stoichiometry. Formation of supersaturated solid solution γ(Fe, Ni) in the solidification and supersaturated intermetallic (Fe,Ni)3(P,B) in the amorphous crystallization indicates that decoupled growth results from solute trapping and disorder trapping in rapid growth of solid solution and intermetallic, respectively. Further application of rapidly quenched experiments and theoretical analysis declare that the decoupled growth results from a competition between the growth of γ(Fe, Ni) and (Fe,Ni)3(P,B), which are controlled by solute trapping and disorder trapping, respectively.

Pure platinum was probed with a nanoindenter fitted with a Berkovich tip to various depths. The indent pattern was made on the as-polished specimen prior to heat treating, after heat treating at 500 °C for 30 min, and again after further heat treating at 1000 °C for 30 min. The variability in the measured hardness decreased as the indentation depth increased from 50 to 300 nm. When the sampled was annealed, the hardness variation was also greater. Increasing hardness variation with decreasing dislocation density and sampling volume indicates that dislocation density plays a critical role in the observed variation, beyond solely instrumentation uncertainty, and supports a defect-based explanation for the stochastic behavior. It appears that the stochastic behavior occurs when multiple dislocations are present in the sampled volume rather than sampling only a single dislocation.

The objective of this work is to reveal the relationship between the molecular structure and shape-memory property of a hydro-epoxy resin system. The system is prepared using hydro-epoxy, menthane diamine (MDA), and poly(propylene glycol) diglycidyl ether (PPGDGE) with different molecular weights. By keeping the PPGDGE content constant, the crosslink density of the shape-memory hydro-epoxy resin system can be changed by varying the molecular weight of PPGDGE. The results indicate that the glass transition temperature (Tg) and rubber modulus (Er) decrease as the crosslink density decreases. The crosslink density has little influence on shape recovery ratio (Rr). Full recovery can be observed after only several minutes when the temperature is equal to or above Tg. However, the crosslink density has a profound effect on the shape fixity ratio (Rf). If the crosslink density is too low, the shape fixity ratio of shape-memory hydro-epoxy resin would not reach 100%.

The nanoindentation fracture behavior of gallium arsenide (GaAs) is examined from two perspectives in two parent papers. The first paper (part I) focuses on in situ nanoindentation within a scanning electron microscope (SEM) and on fractographic observations of cleaved cross-sections of indented regions to investigate the crack field under various indenter geometries. In the second parent paper (part II), cathodoluminescence and transmission electron microscopy are used to investigate the relationship between dislocation and crack fields. The combination of instrumented in situ scanning electron microscopy nanoindentations and cleavage cross-sectioning allows us to establish a detailed map of cracking in the indented region and cracking kinetics for conical and wedge indenter shapes. For wedge nanoindentations, the evolution of the half-penny crack size with the indentation load is interpreted using a simple linear elastic fracture model based on weight functions. Fracture toughness estimates obtained by this technique fall within the range of usual values quoted for GaAs.

A highly biocompatible peptide, triplet repeats of asparagine–serine–serine (3NSS) regulates mineral deposition for the reconstruction of erosive enamel. Healthy human enamel was demineralized to create lesions, then exposed to the 3NSS peptide solution, and finally immersed in artificial saliva. The degrees of nanohardness recovery were 5.02% and 16.27% for the control group and enamel treated with the 3NSS peptide, respectively. Peptides assembling at enamel interrod attracted greater quantities of ions from the solution to form nanocrystalline hydroxyapatite minerals during the reconstruction of vacant gap. This resulted in a decrease in the surface roughness, and the acidic eroded pores were filled completely. Additionally, the newly deposited hydroxyapatites remineralized with the aid of the 3NSS peptide exhibited a smaller average crystalline size, which effectively inhibited plastic deformations. Treatment with the 3NSS peptide provided great improvements in nanohardness and elastic modulus.

The nanoindentation fracture behavior of gallium arsenide (GaAs) is examined from two perspectives in two parent papers. In the first paper (part I), we address the morphology of the crack field induced by different types of indenters by means of in situ nanoindentation inside a scanning electron microscope (SEM) and of cleavage cross-sectioning techniques. In the present paper (part II), we investigate the early stage of crack nucleation under wedge nanoindentation through cathodoluminescence and transmission electron microscopy. We find that the apex angle of the wedge indenter influences the dislocation microstructure and, as a consequence, the mechanism of crack nucleation under nanoindentation. The formation of microtwins depends on both the orientation of the indenter with respect to the orientation of the GaAs crystal and on the apex angle of the indenter. For dicing applications of GaAs wafers, it is desirable to have an opening angle of the indenter smaller than 70° to facilitate the formation of precursor cracks.

The irradiation damage behaviors of single crystal (SC), coarse-grained (CG), and nanograined (NG) copper (Cu) films were investigated under Helium (He) ion implantation at 450 °C with different ion fluences. In irradiated SC films, plenty of cavities are nucleated, and some of them preferentially formed on growth defects or dislocation lines. In the irradiated CG Cu, cavities formed both in grain interior and along grain boundaries; obvious void-denuded zones can be identified near grain boundaries. In contrast, irradiation-induced cavities in NG Cu were observed mainly gathering along grain boundaries with much less cavities in the grain interiors. The grains in irradiated NG Cu are significantly coarsened. The number density and average radius of cavities in NG Cu was smaller than that in irradiated SC Cu and CG Cu. These experiments indicate that grain boundaries are efficient sinks for irradiation-induced vacancies and highlight the important role of reducing grain size in suppressing radiation-induced void swelling.

Under the mixed-mode loading condition, mechanical responses of the Al-terminated O-site Ni(111)/α-Al2O3(0001) interface are investigated using first-principle calculations. The displacement-controlled loadings along 22.5, 45, and 67.5° orientations with respect to the interface are applied. The tension and shear responses of the interface are elaborated according to the computational results, including the mechanical strengths, the effect of tension softening, and the failure characteristic. In addition, the stress versus displacement relationships are derived out based on the general approach suggested by [Sun et al., Mater. Sci. Eng., A170, 67 (1993)], and the deviations between the analytical and computational results are examined in particular. Furthermore, the potential function and its development of this interface are discussed in detail.