A single crystal of NdBa2Cu3O7−δ was synthesized by the Top Seeded Solution Growth method (TSSG method). Then, the crystal was heat-treated 500 °C for 400 h and then 340 °C for 200 h in a pure oxygen gas flow. This sample showed critical current density (Jc) as high as 15,000 A/cm2 under a magnetic field, of 5 T, applied along the c-axis of the crystal. Electron microscopic studies with energy dispersive x-ray spectroscopy (EDS) have revealed that the Ba/Nd ratio fluctuates between 2.0 and 0.7 with a wavelength of a few tens of nanometer. This implies that superconducting phase of Nd1.0Ba2.0Cu3O7−δ and nonsuperconducting phase of Nd1.8Ba1.2Cu3O7−δ mingle with each other, which is the ideal structure for high-Jc superconducting material.

The optical band gap of ZnO films on fused silica in the carrier concentration regime of 1018−1020/cm3 is reported. Contrary to theoretical predictions there is an anomalous increase in the band gap of ZnO films at a carrier concentration of 5 × 1018/cm3, followed by an abrupt decrease at a critical concentration of 3−4 × 1019/cm3 before the optical band gap rises again. Similar observations have been made before, but an explanation of these observations was lacking. We propose a model based on the existence of potential barriers at the grain boundaries, causing quantum confinement of the electrons in the small grains realized in these films. Quantum confinement leads to the initial rise in the optical band gap. On increasing the carrier concentration to the critical value, the potentials at the grain boundaries collapse, leading to the abrupt decrease in the optical band gap. Above this carrier concentration the films behave according to existing many-body theories.

In this Communication we discuss how unimplanted and implanted films (Y and Au implanted) of C60, when hot isostatically pressed (HIPed) at a pressure of 170 MPa (1.7 kbar) of Ar and temperatures of 300 or 400 °C, show substantial uptake of Ar into the film. Rutherford backscattering (RBS) provides an effective method for elucidating film composition, showing the films to have ∼1.5 at.% of Ar, consistent with a stoichiometry close to Ar1 C60. The Ar was found to diffuse from the films when these were held in a vacuum at 300 °C. It could subsequently be reincorporated into the film by re-HIPing, with uptake of a similar amount of Ar. IR spectroscopy showed that the C60 IR absorptions remain unchanged throughout uptake of the Ar and its subsequent loss during heating at 300 °C. It appears that the Ar is trapped interstitially in the films outside the C60 cages.

Nanocrystalline PbS has been grown within a phase-separated oxide glass of composition 10 Na2O, 15 PbO, 17 CaO, 3 Bi2O3, and 55 SiO2 (in mole %) by passing H2S gas over it at temperatures varying from 773 to 943 K. The particle size ranged from 2.5 to 12.9 nm. The dc resistivity of composites of nanocrystalline PbS and the phase separated glass has been measured over the temperature range 300 to 670 K. The resistivity variation in the temperature range 550 to 670 K is characterized by the sodium ion migration in the glass with an activation energy, ∼1.2 eV. The resistivity in the range 300 to 500 K was controlled by conduction in PbS particles with the estimated band gap showing an increase with a decrease in the particle size.

The crystallographic structures of some phases present as precipitates in Al–Li–Cu–Mg alloys are not perfectly resolved. In particular, several structural models have been proposed for the S′ phase, and this controversy is not yet resolved. New x-ray powder diffraction measurements have been performed to compare the theoretical powder diffraction patterns associated with each proposed model with the measured spectra obtained from two different kinds of alloys. The structural model of the S′ phase described by Mondolfo [L. F. Mondolfo, Aluminum Alloys Structure and Properties (Butterworths, London, 1976)] agrees with the experimental results and allows us to reject the two other proposed crystallographic models.

Three natural type IIa diamond crystals were used for forced diffusion of boron. The diffusion was performed under bias otherwise with the same conditions. The boron diffusion coefficient in diamond was found to be 8.4 × 10−15 and 4 × 10−14 cm2/s at 1000 °C, depending on the direction of the electric field. The drift velocity of boron in diamond under 850 V at 1000 °C was found to be about 1.2 × 10−8 cm/s.

When undercooled molten Cu30Ni70 crystallizes at an undercooling ΔT≅ 145 K (ΔT is defined as Tl – Tk where Tl is the liquidus of Cu30Ni70 and Tk is the kinetic crystallization temperature), its grain size undergoes a rapid decrease by as much as two orders of magnitude in a narrow temperature range. This phenomenon is termed grain refinement. It was found that grain refinement is brought about by multiplication of dendrites. Composition analysis of the dendrite indicates that it has the least Ni concentration at its axis. The Ni content then increases radially from the central axis. Therefore, the dendrite is unstable against melting since the melting temperature of Cu–Ni increases with Ni content. The origin of grain refinement is attributed to the remelting of these dendrites.

Numerical results on the evolution of thermal stresses in multilevel interconnects are presented. Two levels of aluminum lines with an aspect ratio of unity, aligned vertically or arranged in a staggered manner, are considered by recourse to the finite element analysis. The stresses are found to be significantly higher in the lower-level lines than in the upper-level lines, for both the aligned and staggered arrangements. The stress magnitudes are generally smaller in lines of staggered arrangement, compared to the case of aligned lines. Implications of the present findings are discussed, with directions of future studies highlighted.

A Dy2O3 single crystal has been used as a seed for the growth of isothermally melt-textured Dy-123 material. The nucleation-controlled step has been observed to be related to the heterogeneous nucleation of 211 particles at the surface of the dysprosium oxide single crystal. The subsequent growth mode seems to be controlled by a high concentration gradient of dysprosium in the liquid phase. This leads to a directional solidification process of the 123 phase. The size of the 211 particles seems to decrease as the distance from the dysprosium oxide single crystal increases.

We review the synthesis methods and properties of single crystal, powder, and thin film TlBaCaCuO high-temperature superconducting (Tl-HTS) materials. With transition temperatures ≥ 100 K for several compounds, Tl-HTS materials present real opportunities for applications above 77 K. Experiments using (1) single crystals: determined precise structural parameters and identified the complex Tl1+–Tl3+ equilibrium model; (2) powders: studied the complex thermodynamic phase diagram; and (3) epitaxial films: studied fundamental properties such as electron pair symmetry and the effect of controlled extrinsic defects on flux pinning strength, as well as providing the large-area surfaces required for device applications.

The passivation of the nitrogen top-layered (100) surface of cBN by hydrogen was theoretically predicted recently to be related to the difficulty of chemical vapor deposition of cubic boron nitride. The possibility of photochemical depassivation of this surface was suggested by the anti-bonding nature of the surface H–N bonds at the lowest unoccupied molecular orbital; that was demonstrated by AM1 molecular orbital calculations using large cBN clusters such as B30N32H64(2+) and B30N32H62 (2BH3).

A new essentially nondestructive cross-sectional method is described for measuring the individual thicknesses of multilayer YBa2Cu3O7 (YBCO) and SrTiO3 (STO) thin films using off-axis ion milling and the atomic force microscope (AFM). Since the ion-milling is done during routine patterning of a thin-film device and the AFM requires only a small area for imaging, no additional sample preparation is required. This is a significant improvement over traditional cross-sectional techniques which often require lengthy and destructive sample preparation. Also, there is no a priori reason that this technique would not be amenable to other multilayer thin-film systems.

The subsolidus phase relationships of the high-Tc 2223 superconductor in the (Bi, Pb)–Sr–Ca–Cu–O (BSCCO) system have been examined at 810–820 °C. All experiments were carried out at ambient pressure in a 7.5% O2 (92.5% Ar) atmosphere. Eleven phases were found to exist in equilibrium with the 2223 phase. These 11 phases include CuO and 10 oxide solid solutions. From among these phases, a total of 48 five-phase combinations including the 2223 and 2212 phases were investigated experimentally, and 16 equilibrium assemblages were found which define a multicomponent compositional space corresponding to the 2223 + 2212 solid-state compatibility region. The subsolidus data form a partial basis for future investigation of the Pb-2223 primary phase field.

We report a novel method for the synthesis of carbon nanotubes: low temperature solid pyrolysis. By pyrolysis of hexamethyldisilazane-derived silicon carbonitride powders in a graphite furnace, we synthesized carbon nanotubes at 1400 °C. This new method has advantages of in situ growth of the carbon nanotubes, is stable in the synthesis process, and is technically simpler than conventional arc-discharge methods.

The stoichiometric intermetallic compound NbSi2 has been synthesized by mechanical alloying (MA) elemental Nb and Si powders. The alloying process has been investigated by means of x-ray diffraction (XRD) and differential scanning calorimetry (DSC). It was found that the formation of the Nb2Si intermetallic compound occurs abruptly after 65 min of milling without any interruptions during the alloying process. However, short interruptions at a 5 min interval during ball milling result in a gradual reaction for the formation of the NbSi2 compound as well as a new metastable bcc structured solid solution. We conclude that the temperature rise during mechanical alloying plays an important role in initiating the abrupt reaction after an incubation milling time.

The microstructure of the disproportionated NdFeCoZrB alloy during the solid-HDDR (hydrogenation-disproportionation-desorption-recombination) process was investigated by means of scanning electron microscope (SEM) and transmission electron microscope (TEM). Except for a similar colony-type structure to ternary alloy, fine particles including spherical (Fe, Co)2B phase and undecomposed rim-like Nd2(Fe, Co)14B compound were found dispersed within the α–(Fe, Co) matrix of the microstructure of the disproportionated NdFeCoZrB alloy. An unknown Fe-rich phase with a comparable size to that of the matrix grain was also detected by electron diffraction. These results strongly suggest that the undecomposed rim-like Nd2(Fe, Co)14B particles are probably the memory sites for the origin of anisotropy of the received NdFeCoZrB materials.

Internal friction and Mössbauer techniques have been used to investigate the structure of C–Cr associates and the arrangement of Fe atoms near them in the Cr martensitic steel MANET subjected to different thermal treatments. After slow rate cooling from the austenitic field, the Mössbauer spectra exhibit, besides the complex magnetic pattern of martensite, a low intensity singlet attributed to the presence of a Cr-rich bcc phase. In correspondence, the internal friction curves, show, among others, a Snoek-type peak due to anelastic processes involving C–Cr associates with 6 Cr atoms. To explain the experimental results, a simple structural model is suggested.

Formation of nanocrystalline Fe–4 wt.% Al solid solution has been achieved through SPEX ball milling of blended elemental Fe and Al powders. Differential scanning calorimetry (DSC) and x-ray diffraction (XRD) have been employed to follow the structural evolution during the ball-milling process. Exothermic peaks exhibited in DSC diagrams of the powders milled for 10 to 60 min yielded thermal enthalpies corresponding to the formation of Fe–4 wt.% Al solid solution, from which the kinetics of formation were found to follow the Johnson–Mehl–Avrami equation. Assessment of the kinetic parameter n reveals a diffusion controlled mechanism, in which grain and interphase boundaries may play a crucial role, during the solid solution formation of Fe–4 wt.% Al.

Effects of electroless nickel plating on resistivity-temperature (R-T) characteristics of (Ba1-xPbx)TiO3 thermistor were studied. Comparison experiments showed that not only the permeation of plating solution, but also the reaction of electroless nickel plating influences the positive temperature coefficient (PTC) effect, and that the two effects are different in nature. It is first proposed in this paper that hydrogen atoms generated in electroless nickel plating may reduce components of PTC ceramics.

Dislocations have been observed in deformed Cu/Nb nanolayer composites of wavelength 17 and 7 nm. The dislocations thread through the Cu/Nb interfaces even though there is a change of Burgers vector. Conventional and high resolution transmission electron microscopy studies show that the in-plane bowing direction of these dislocations in the Cu layers is opposite to that in the Nb layers, so that the dislocations appear to zig-zag. These observations are explained by the presence of residual tensile stresses in Cu and residual compressive stresses in Nb, which make dislocations bow in opposite directions in the alternating layers.