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A processing route has been developed to grow bundles of carbon nanotubes on substrates from methane and hydrogen mixtures by microwave plasma-enhanced chemical vapor deposition, catalyzed by iron particles reduced from ferric nitrate. Growth takes place at about 900 °C leading to nanotubes with lengths of more than 20 μm and diameters on the nanometer scale.

In the primary soot produced by arc discharge using an yttrium carbide loaded anode, bundles of single‐walled carbon nanotubes (SWT) are observed, protruding radially from YC2 particles coated with graphitic multilayers. The graphitic cages separating YC2 particle and SWT bundles fall into the narrow range of 10–20 layers. The morphology of the clusters suggests a two‐step growth model: The radial SWT growth pattern is first initiated by catalytic action between the YC2 droplet and the carbon in the gas phase. Second, and upon cooling, the graphitic cage starts by segregating excess carbon from the YC2 bulk, arresting further growth of SWT.

We report here on the high‐density preparation of single‐wall tubes in the presence of mixed catalysts of the types Fe/Ni and Co/Ni, in the soot as well as in the weblike deposits forming in the chamber. The yield is much higher than previously reported, and gram quantities can be obtained. Diameters cover the range from 0.9 to 3.1 nm, larger than previously reported, with the histogram showing only one peak at 1.7 nm. Evidence of an epitaxial action between C60 and single‐walled nanotubes is presented. Results from the mixed catalysts Co/Cu, Ni/Mg, and Ni/Ti are also reported.

Characterization of the arc‐discharge deposits at the cathode from anodes containing yttrium oxide and titanium by transmission electron microscopy and x‐ray diffraction shows different results with respect to an encapsulation of the metal carbides into carbon clusters. Yttrium carbide is encapsulated into carbon nanoclusters in a crystalline phase. The formation of titanium carbide, on the other hand, preempts the formation of the carbon—carbon bonds necessary to form the carbon cages, so that only titanium carbide clusters are observed. Thermodynamic data support the interpretation of the results.

We describe the controlled patterning of nanopores in graphene layers by using the low-energy (

In order to extend the potential applications of medical ultrasonic array transducers, two optimized directions with the maximal electromechanical coefficient k33′ and minimal k31 are determined for [001] and [110] poled 0.71Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 single crystals using the experimental method. The maximum values of k33′ can reach 92.8% and 93.3%, respectively, corresponding to [001]W/[110]L and [110]W/[1–11]L cuts. Furthermore, we simulate the performances of three 3.5 MHz linear array transducers based on the determined directions by PIEZOCAD. Results indicate that under the [001]W/[110]L direction, 25% broader bandwidth, 40% shorter pulse length, and 3 dB higher sensitivity can be obtained compared to the traditional Pb(Zr1−xTix)O3 transducers.

To enhance the service temperature of relaxor-PbTiO3 pyroelectric single crystals, high quality ternary perovskite single crystal was grown by a modified Bridgman technique. Analyzed by x-ray fluorescence, the as-grown crystal is 0.41Pb(In1∕2Nb1∕2)O3–0.17Pb(Mg1∕3Nb2∕3)O3–0.42PbTiO3 [PIMNT(41/17/42)], which appears to be a tetragonal ferroelectric phase with relatively high Curie temperature of 253°C. It exhibits the relative permittivity of 487 and low dielectric loss of 0.3% at 50Hz and room temperature. The pyroelectric properties with a pyroelectric coefficient of 5.7×10−4C∕m2K and a detectivity of 6.34×10−5Pa−1∕2 would satisfy the needs of operation as a high Curie temperature material. The results show that PIMNT crystal with better temperature stability, compared with the pure PMNT single crystals, is a good candidate as an infrared detector material.

In order to better utilize the superior transverse piezoelectric properties of [011] poled (1−x)Pb(Mg1∕3Nb2∕3)O3–xPbTiO3 single crystals with the composition near the morphotropic phase boundary, a complete set of elastic, dielectric, and piezoelectric constants of [011] poled 0.71Pb(Mg1∕3Nb2∕3)O3–0.29PbTiO3 single crystal was measured by ultrasonic and resonance methods at room temperature. The electromechanical coupling coefficient k32 and transverse piezoelectric constant d32 can reach 0.94 and −1883pC∕N, respectively. This complete set of material properties will provide convenience for device designs and fundamental theoretical studies.

The dielectric and piezoelectric properties of the Mn-doped 0.71Pb(Mg1∕3Nb2∕3)O3–0.29PbTiO3 (PMNT) crystals oriented along ⟨001⟩ and ⟨110⟩ directions, respectively, have been investigated. The investigations have shown that 3at.% Mn substitution results in (i) a large increment of coercive field at the cost of piezoelectric response, (ii) an increased Curie temperature and an enhanced stability of the ferroelectric rhombohedral phase, which enable a wider operation temperature range, and (iii) enhanced linearity in electric field induced strain with lower hysteresis. The hardened PMNT crystals favor their applications in high power transducers.