Composite formation between carbon nanotubes and polymers can dramatically enhance the electrical and thermal properties of the combined materials. We have prepared a composite from polystyrene and multi-walled carbon nanotubes (MWCNT) and, unlike traditional techniques of composite formation, we chose to polymerize styrene from the surface of dithiocarboxylic ester-functionalized MWCNTs to fabricate a unique composite material, a new technique dubbed “gRAFT” polymerization. The thermal stability of the polymer matrix in the covalently linked MWCNT-polystyrene composite is significantly enhanced, as demonstrated by a 15 °C increase of the decomposition temperature than that of the noncovalently linked MWCNT-polystyrene blend. Thin films made from the composite with low MWCNT loadings (<0.9 wt%) are optically transparent, and we see no evidence of aggregation of nanotubes in the thin film or solution. The result from the conductivity measurement as a function of MWCNT loadings suggests two charge transport mechanisms: charge hopping in low MWCNT loadings (0.02–0.6 wt%) and ballistic quantum conduction in high loadings (0.6–0.9 wt%). The composite exhibits dramatically enhanced conductivity up to 33 S m−1 at a low MWCNT loading (0.9 wt%).

Solid-state wetting experiments were carried out to derive the work of adhesion (adhesion energy) of pertinent Cu/liner interfaces via the Young–Dupré equation using contact-angle measurements of the Cu equilibrium crystal shape on Ta and TaNx liners. Four types of liner surfaces were examined: untreated sputtered Ta (uSp-Ta), untreated sputtered TaNx (uSp-TaN), untreated atomic layer deposited (ALD) TaNx (uALD-TaN), and indium surfactant-treated ALD TaNx (tALD-TaN). All Cu-liner stacks were subsequently annealed at 600 °C for 48 h in a forming gas (95% Ar/5% H2) ambient. For Cu/uSp-Ta, the work of adhesion was found to be 2170 mJ/m2, corresponding to an average contact angle of 74°, while for Cu/uSp-TaN, the work of adhesion amounted to 1850 mJ/m2 for an average contact angle of 85°. Alternatively, the work of adhesion for Cu/uALD-TaN was determined to be 1850 mJ/m2, corresponding to an average contact angle of 85°, while for Cu/tALD-TaN, the work of adhesion was 2280 mJ/m2, at an average contact angle of 70°. These findings indicate that the highest degree of surface wetting occurs for the indium surfactant-treated ALD TaNx. It is thus suggested that surfactant treatment causes a reduction in the energy barrier to Cu nucleation, resulting in an enhancement in Cu wetting characteristics and a more uniform concentration of Cu nucleation sites. A critical potential outcome is the formation of atomically smooth Cu-liner interfaces with enhanced adhesion characteristics.

Many layered ternary ceramics displayed unusual thermal shock behavior, i.e., the retained strengths of as-quenched samples increased with increasing quench temperature above a critical quench temperature. However, the causation was not clear even though this phenomenon has been observed for 10 years. In this study, the thermal shock behavior of Ti3SiC2 and Ti3AlC2, two representative members of layered ternary ceramics, was investigated. The results indicated that the formation of surface oxides was responsible for this abnormal phenomenon. These results might contribute to the understanding of this unusual behavior of other layered ternary ceramics.

The cementum–enamel junction (CEJ) is a unique interface that plays a critical role in effectively transferring force from the top of the tooth to the jawbone. A comparative study of bovine and equine teeth has been carried out experimentally to establish the relationship among the interfacial structure, fracture resistance, and mechanical functions. The CEJs were analyzed by optical microscopy and scanning electron microscopy (SEM). Microhardness and elastic modulus were measured with a Vickers microhardness tester and a nanoindentation system. A modified cantilever beam technique was used to study CEJ fracture process and the toughness (Gc,). It was observed that CEJ is a distinct interface connecting the hard enamel (200–350 kg/mm2) with the soft cementum (∼20–30 kg/mm2). Bovine CEJ was macroscopically flat and smooth. However, under SEM, a close integration of cementum bumps and enamel pits at the 5 μm level and dimples at the 200 nm level were clearly seen. In equine CEJ, the similar flat cementum–enamel interface was interrupted by hemispherical cementum protrusions (average size of 28.3 μm) at high density (340/mm2). Despite the microscopic roughness, bovine CEJ was easy to fracture at relatively low toughness (128 J/m2). The measured toughness for equine CEJ was about seven times that of bovine (1140 J/m2). The high toughness has been attributed to the mechanical interlocking provided by the cementum protrusions. The underlying crack bridging mechanism and the applications to the design of orthopaedic implants are briefly discussed.

The effect of surface interaction on nanoindentation testing using a rigid conical indenter is analyzed. A relation between the indentation depth and the indentation load is established as a function of the adhesion energy between the indenter and the surface of an elastic material. A closed-form solution of the contact stiffness for adhesive contact is obtained. The contact stiffness in the presence of surface interaction is always less than that for contact without surface interaction at the same indentation depth, while it is always larger than that for adhesion-less contact subjected to the same indentation load. A lower bound is established, which determines the working zone to operate to avoid the effect of surface interaction in the characterization of the contact modulus.

The plane-strain bulge test is used to investigate the mechanical behavior of freestanding electroplated Cu thin films as a function of film thickness and microstructure. The stiffness of the films increases slightly with decreasing film thickness because of changes in the crystallographic texture and the elastic anisotropy of Cu. Experimental stiffness values agree well with values derived from single-crystal elastic constants and the appropriate orientation distribution functions. No modulus deficit is observed. The yield stress of the films varies with film thickness and heat treatment as a result of changes in the grain size of the films. The yield stress follows typical Hall-Petch behavior if twins are counted as distinct grains, indicating that twin boundaries are effective barriers to dislocation motion. The Hall-Petch coefficient is in good agreement with values reported for bulk Cu. Film thickness and crystallographic texture have a negligible effect on the yield stress of the films.

CeO2 thin films as insulating layers for high-temperature superconducting digital devices were studied. The dependence on substrate temperature and oxygen pressure of the surface morphology and crystallinity of CeO2 thin films prepared by pulsed laser deposition were investigated. CeO2 thin films with a flat and closely grained surface were obtained at a relatively low oxygen pressure of 3.6 Pa, whereas higher oxygen pressure led to CeO2 thin films with a rough surface and columnar grains. The recovery of oxygen content in superconducting layers was examined for multilayer structures with CeO2 thin films. Enough oxygen was supplied to the upper and lower superconducting layers when the multilayer was cooled slowly in 3 × 10−4 Pa oxygen pressure after deposition. Resistively shunted junction type I-V characteristics were confirmed for interface-engineered ramp-edge junctions in a multilayer structure including four superconducting layers with CeO2 thin films.

The affiliations for the authors were cited incorrectly in the November 2005 issue of the Journal of Materials Research. The correct affiliations appear above. The printer regrets this error.

Sn–Zn-based alloys are promising low melting-point Pb-free solders, and it has been reported that their wetting properties and oxidation resistance can be improved with the addition of Cu. The interfacial reactions in the Sn–9 wt% Zn–xCu/Cu couples at 250 °C and Sn–9 wt% Zn–xCu/Ni at 280 °C were examined in this study. A thick γ–Cu5Zn8 phase layer and a very thin β′–CuZn phase layer were formed in both the Sn–9 wt% Zn/Cu and the Sn–9 wt% Zn–1 wt% Cu/Cu couples. The γ–Ni5Zn21 phase layer was formed in both the Sn–9 wt% Zn/Ni and Sn–9 wt% Zn–1 wt% Cu/Ni couples. With longer reaction time, the δ–Ni3Sn4 phase were formed in the Sn–9 wt% Zn/Ni couple as well. In both the Cu and Ni couples, the Zn-containing γ phases were uniform and planar and were the dominant reaction products. However, when the Cu content of the Sn–9 wt% Zn–xCu solders was 10 wt%, the interfacial reaction product becomes the η–Cu6Sn5 phase in both the Cu and Ni couples.

The formation enthalpies from the oxide end-members (ΔHf,ox) of the CeO2–MO1.5 (M = La, Gd, and Y) systems were determined by high temperature oxide melt drop solution calorimetry. In each system, ΔHf,ox is slightly positive over the investigated composition range with a maximum at a certain doping level. Above that concentration, ΔHf,ox decreases rapidly and stays almost constant. Such behavior is strikingly different from the strongly negative ΔHf,ox of the ZrO2–YO1.5 and HfO2–YO1.5 systems. The absence of substantial energetic stabilization in the CeO2–MO1.5 systems may be attributed to the large size of Ce4+, which has no preference for 7-coordination like the smaller Zr4+ or Hf4+ ions. The primary defect associates in CeO2–MO1.5 are proposed to be neutral trimers with oxygen vacancies nearest neighbor to the dopant cations. It is also suggested that the maximum ΔHf,ox (destabilization) of CeO2–MO1.5 is determined by the local site distortion rather than the global lattice deformation. The relatively stable region after the maximum ΔHf,ox may be attributed to the somewhat stabilizing long-range defect–defect interactions, which become effective above a certain doping level.

To investigate the effect of plasma-incorporated fluorine on Si donors in pseudomorphic-high electron mobility transistors (P-HEMTs), we used x-ray photoemission spectroscopy to analyze three layers near the Si δ-doped layer and the Si δ-doped layer itself, in which we previously found fluorine accumulation after post-thermal annealing following fluorocarbon-based plasma exposure. For this evaluation, we developed controllable and low-speed AlGaAs wet-chemical etching using citric-acid-based wet etchant. We used it to expose one of the layers to be analyzed: one 7.5 nm above the Si δ-doped layer, one 1.5 nm above it, the δ-doped layer itself, and one 1.5 nm below it. We found that the accumulated fluorine localized in the δ-doped layer and reacted with Si donors. This is apparently the main reason for the carrier passivation in the fluorocarbon-based plasma-exposed P-HEMTs.

A CoFe2O4 particle/organic hybrid was synthesized using in situ processing of metalorganics of cobalt and iron below 100 °C. A mixture of cobalt (II) acetylacetonate (CA) and iron (III) 3-allylacetylacetonate (IAA) was hydrolyzed and polymerized yielding cobalt ferrite particle/organic hybrid. The crystallinity of cobalt ferrite depended upon the hydrolysis conditions of cobalt acetylacetonate-iron 3-allylacetylacetonate (CA-IAA). Nanocrystalline cobalt ferrite particles were uniformly dispersed in the organic matrix. The saturation magnetization of hybrid increased with increasing crystallinity of cobalt ferrite particles in the organic matrix. The hybrid showed a magnetization-applied field (BH) curve with no coercive force at room temperature. The magnetization versus H/T curves from 150 to 300 K were superimposed on the same curve and satisfied the Langevin equation. The hybrid revealed a saturation magnetization of 33.7 emu/g and a coercivity of 11 kOe at 4.2 K.

TiO2 thin films were prepared with a spinodal phase separation structure ranging from hundreds of nanometers to micrometers in size by the sol-gel dip-coating method from a titanium tetraisopropoxide solution containing polyoxyethylene (20) nonylphenyl ether (NPE-20). It was possible to change the titania domain size of the spinodal phase separation structure by selecting alcohol as the solvent because the polycondensation and the phase separation are severely influenced by its evaporation rate from the surface of the coated film. It was also observed that the titania domains became larger in size as the film thickness increased in the bottom area of the substrate when the dip-coating method was applied, while uniformly sized titania domains were possibly formed by a spin-coating method. Furthermore, the contrast between the TiO2 phase and the air phase was not sharp when the titania domain size was smaller than several hundreds of nanometers. It was possible to prepare TiO2-air interconnective films with the spinodal phase separation structure 200–300 nm in domain size by subsequent HF etching. In addition, combining spinodal phase separation structure (SPSS) TiO2 thin film with different skeleton size has the potential to create TiO2 thin film with high photo-electron conversion efficiency due to its particular structure, higher surface area, and lack of bottleneck for electron transfer.

A novel red emitting phosphor, Eu3+-doped Ba2SnO4, has been synthesized by solid-state reaction. Photoluminescence (PL) excitation spectrum of Ba2Sn0.925Eu0.075O4 shows the strongest broad band from 220 to 280 nm due to the charge transfer (CT) band of Eu3+–O2−, and the band centered at 180 nm could be caused by the CT band of Ba2+–O2−. The band (110–130 nm) could be attributed to SnO68− octahedron band absorption. It is found that under 254 nm excitation, Ba2Sn1−xEuxO4 (0.025 ≤ x ≤ 0.125) exhibits a strong emission at around 592 nm, and with the increase in Eu3+, the phosphors present orange to red luminescence due to the decreasing of the site symmetry of Eu3+. The maximum PL intensity has been obtained for 7.5 mol% concentration of Eu3+ in Ba2SnO4. On the other hand, under 147 nm excitation, the phosphors do not emit effectively because of inefficient absorption in vacuum ultraviolet (VUV) region.

The Aurivillius phases in the vicinity of the Bi5AgNb4O18 compound were determined by means of solid-state reaction, x-ray diffraction, and scanning electron microscopy. The stoichiometric Aurivillius phase Bi5AgNb4O18 is compatible with Ag/Ag2O, BiAgNb2O7, and BiNbO4. Two Aurivillius-phase solid solutions were found for the A-site-deficient Bi5+x/3Ag1−xNb4O18 and the oxygen-deficient Bi5−zAgzNb3O15−z. The x value of the Bi5+x/3Ag1−xNb4O18 solid-solution limit is between 0.2 and 0.4. A single-phase non-stoichiometric compound was obtained for x = 0.2 in Bi5+x/3Ag1−xNb4O18 and z = 0.25 in Bi5−zAgzNb3O15−z. The dielectric (at 1 MHz), ferroelectric, and piezoelectric properties of the stoichiometric Aurivillius phase Bi5AgNb4O18 were as follows: TC= 772 °C, ϵr= 197 (room temperature), ϵmax = 830, tanδ ∼ 10−3(room temperature to 540 °C), Pr = 6μC/cm2, Ec = 52kV/cm, d33 = 11pC/N.

We present a unique approach combining biological manipulation with advanced imaging tools to examine silica cell wall synthesis in the diatom Thalassiosira pseudonana. The innate capabilities of diatoms to form complex 3D silica structures on the nano- to micro-scale exceed current synthetic approaches because they use a fundamentally different formation process. Understanding the molecular details of the process requires identifying structural intermediates and correlating their formation with genes and proteins involved. This will aid in development of approaches to controllably alter structure, facilitating the use of diatoms as a direct source of nanostructured materials. In T. pseudonana, distinct silica morphologies were observed during formation of different cell wall substructures, and three different scales of structural organization were identified. At all levels, structure formation correlated with optimal design properties for the final product. These results provide a benchmark of measurements and new insights into biosilicification processes, potentially also benefiting biomimetic approaches.