Carbon nanotube (CNT)-reinforced magnesium (Mg) matrix composites were synthesized using a powder metallurgical method and tested compressively along the plane normal and in-plane orientations. Yield strengths of composites were significantly increased by 35–129% compared with that of pure Mg. With the increase of CNT weight percentage, yield strength first increased until reaching a critical CNT weight percentage and then decreased. Twinning operated in the in-plane samples when CNT weight percentage was less than or equal to 0.5%, whereas twinning operation was not observed in all plane normal samples and the in-plane samples with 1% or higher CNT weight percentage. Severe plastic deformation was exhibited in fracture surface images with low magnification, whereas intrinsic brittle fracture feature was observed under high magnification. A theoretical model incorporating the Orowan strengthening and the thermal expansion mismatch strengthening was utilized and made good yield strength predictions.

Recently, the {10-12} twin variants activated during dynamic plastic deformation (DPD) of Mg alloy have been investigated by analyzing their Schmid factors (SFs), and their contributions to deformation have been calculated. During DPD of Mg–3%Al–1%Zn alloy, different {10-12} variants are generated relative to their SFs when initial grains have defined orientations with one a-axis of the crystal lattice at roughly 0 or 30° from the compression direction. The volume fraction of twins deeply influences the strain accommodated by twinning. The {10-12} variant pair with the maximum SF accommodated about 90% of the twinning strain. Its high volume fraction indicated that both nucleation and growth mechanisms played important roles in the strain accommodation. Other {10-12} variants had a lower volume fraction and accommodated twinning strain mainly by twin nucleation and made a lesser contribution to the total deformation.

Solidification of undercooled Ni–3.3 wt% B alloy melt was investigated by glass fluxing. If ΔTe < 140 ± 10 K, two recalescences appear, indicating that stable eutectic reaction occurs; if ΔTe ≥ 140 ± 10 K, three recalescences can be observed, indicating that metastable eutectic reaction occurs. Analysis indicates that the phase fractions of the as-solidified structure can be predicted by the recalescence delay times in the cooling curves. High-speed video images show that the solidification interface of primary solidification changes from single dendritic shape to spherical shape with increasing ΔTp; the interface of eutectic solidification changes from many small “dendrites” to a single large one with increasing ΔTe; the interface of residual liquid solidification changes from many small rings to a single large one with increasing ΔTr. The growth velocity of eutectic solidification suggests a coupled growth at small and moderate undercoolings and decoupled growth at large undercooling, whereas that of residual liquid solidification cannot be interpreted by the available models.

By taking the machine stiffness into the classic Hertzian solution rather than assuming a constant machine stiffness, we developed an approach to simultaneously derive the spherical indenter tip radius and machine stiffness in arbitrary ranges of loads and indenter radii. In contrast, the direct Hertzian fitting method tends to underestimate the radius, especially for larger indenter tips. The success is based on indention tests on two materials with known material stiffness, and the displacement difference under the same load is not affected by the machine stiffness. A total of eight spherical indenter tips with the radii ranging from a few microns to hundreds of microns have been indented on fused silica and single crystal sapphire. Our method gives correct indenter radii for all indenters. The machine stiffness is found to indeed vary with the indentation load and indenter radius. This method has many potential applications in the area of nano-indentation with spherical indenters, such as indentation size effect, modulus and hardness measurement, and micropillar testing.

Nanoscale metal–insulator–metal (MIM) diodes consisting of a nanoscale-thickness insulator layer sandwiched between two dissimilar metal layers offer the potential for very high frequency alternating current to direct current signal rectification. Active nanoscale tuning of electronic tunneling through the insulator layer to form point contact diodes has previously been limited to barriers composed of soft organic films due to the force limitations of conductive-atomic force microscopy. In this paper, MIM diodes with oxide-based insulators are formed in situ with sub-nanometer depth precision and characterized using a nanoindenter equipped with electrical testing capabilities. Simultaneous measurement of both electrical and nano-mechanical information is accomplished in an MIM stack of the form Nb/Nb2O5/boron-doped diamond nanoindenter tip. Using this technique, we show that the diode behavior can be electromechanically tuned over a range of more than 1 V at equivalent currents via small changes in indentation depth and the results can be modeled using a Fowler–Nordheim approximation.

This work attempts to optimize past research results on lead zirconate titanate (PZT) using the fabrication processes at the U.S. Army Research Laboratory so as to achieve a high degree of {001} texture and improved piezoelectric properties. A comparative study was performed between Ti/Pt and TiO2/Pt bottom electrodes. The results indicate that the use of a highly oriented {100} rutile phase TiO2 led to highly textured {111} Pt which in turn improved both the PTO and PZT orientations. PZT (52/48) and (45/55) thin films with and without PTO seed layers were deposited and examined via x-ray diffraction (XRD) methods as a function of annealing temperature. The seed layer provides significant improvement in the {100} orientation generally, and in the {001} subset of planes specifically, while suppressing the {111} orientation of the PZT. Improvements in the Lotgering factor (f) were observed from an existing Ti/Pt/PZT process (f = 0.66) to samples using the PTO seed layer deposited onto the improved Pt electrodes, TiO2/Pt/PTO/PZT (f = 0.96).

Ca3Co4O9 and Ca2.8Bi0.2Co4O9 thin films were fabricated on LaAlO3 (LAO) substrate using pulsed laser deposition technique and were studied for their thermoelectric (TE) properties in Stranski–Krastanov mode for the first time. The thin films consisted of 3D clusters/islands on a ∼14-nm thick 2D layer with cluster density being higher for Ca2.8Bi0.2Co4O9 thin films. The clusters also represent areas of dislocation and therefore act as carrier scattering centers, which leads to a temperature-activated type conductivity. Seebeck coefficient as high as 136 and 163 μ V/K was measured for the Ca3Co4O9 and Ca2.8Bi0.2Co4O9 thin films, respectively, which is among the highest reported values for this system. The 3D island formation was also found to be useful in reducing the thermal conductivity of the thin film/substrate system by increased phonon scattering. This work shows that the island formation in thin films can be utilized as a means of enhancing TE properties of a thin film system, however, a detailed work including optimization of the film thickness and cluster/inland density is required.

A new strategy using hyperbranched poly(amidoamine)s to functionalize CdTe quantum dots (QDs) has been described. Hyperbranched poly(amidoamine)s with amine terminals (HP-EDAMA1) were synthesized by one-pot polymerization via the coupled-monomer method and subsequently used to functionalize preformed CdTe QDs. Quite different from previous studies in which the photoluminescence of QDs was quenched by further functionalization with tailored ligands, the quantum yield of CdTe/HP-EDAMA1 nanocomposites was 2 times that of pure CdTe QDs without modification. With this versatile method, the photoluminescence quenching of QDs in the modification process by matrix materials can be effectively solved and new QDs/hyperbranched polymer nanocomposites with potential applications in biomedicine might be offered.

Visible light emitting ZnO quantum dots (QDs) were synthesized by a modified sol–gel method and in situ coated with the amino acid cysteine to modify their surface chemistry and govern the crystal growth process. Surface chelation by a hydrophilic thiol such as cysteine offered a fine control over the particle size and modulated the optical emission and its stability by reducing the density of surfacial oxygen deficiencies and also induced the formation of hierarchical nanostructures in the solution. TEM and XRD results confirmed the formation of mono-dispersed and spherical ZnO QDs in the size range 2.5–3.8 nm. The modulation of band gap energies was manifested in the visible emission of cysteine modified QDs, which was found to be remarkably stable for cell labeling applications, when compared to the photoluminescence of conventional ZnO QDs.

This work reports the preparation of iron-doped alumino-phosphate glass using microwave (MW) radiation at 1723 K in comparision with a conventional resistance heating furnace at the same temperature. X-ray diffraction analysis of the sample prepared in an MW furnace has confirmed glass formation which is similar to that of glass prepared in an electric furnace. Glass transition temperatures (Tg) for MW and conventional melted glass samples were observed to be 866 and 873 K, respectively. Higher Fe2+/(Fe3+ + Fe2+) ratio was reported in glass prepared in the MW furnace compared with the conventional furnace. The Fourier transform infrared spectra for both the samples indicate identical nature. It was observed that the maximum power required for melting glass in MW heating was 0.85 kW, which is around 25–30% of the power consumed by the conventional resistance heating furnace. In addition, the time needed to melt the glass in the MW furnace was found to be 3–4-fold lesser than the time required in the resistance heating furnace.

Molybdenum trioxide nanostructures were synthesized, to make highly friction resistant molybdenum disulfide, by low temperature hydrothermal reaction without using any template or catalyst. The as-synthesized materials were sulfided with H2S at 400 and 800 °C. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier-transform infra-red spectroscopy, and thermogravimetric analysis were used for the physical characterization of the materials. The oxide material is highly crystalline with unique morphology. The factors affecting the size and shape of the synthesized materials were studied in detail. The crystalline nature of the materials decreased after the sulfidation process at 800 °C without any change in morphology. The wear resistance and lubricity of the material were studied under harsh conditions. The comparative study of these materials with MoS2 prepared by the hard templating method (using mesoporous silica template) reveals that the new material synthesized by direct hydrothermal route is pure phase and has better wear resistance and antifriction properties. Ultra high stability of the material is the most distinguished property of the material synthesized.