A new method was developed allowing large superconducting YBa2Cu3O7 (YBCO) monoliths having complex shapes to be obtained. This method consists of joining two or more YBCO monoliths, and it is based on the interfacial melting induced by metallic Ag thin foils inserted between YBCO pellets. Studies of the microstructure and the superconducting properties of the joints obtained by using this technology have shown that a perfect interface can be obtained without agglomerations of non-superconducting phases and with a critical current density as high as that of the original blocks. No evidence of Ag precipitates was detected either at the interface or into the YBCO solid matrix, suggesting a migration of Ag. For a better understanding of the interface growth mechanism, we studied the influence of the cooling rate. The knowledge on the Ag diffusion process has enabled us to propose a model for the growth mechanism of the YBCO/Ag/YBCO interfaces.

Single-walled carbon nanotubes (SWNTs) were successfully synthesized by pyrolysis of pyridine over MgO supported Fe–Mo or Co–Mo catalysts in the presence of pure H2 or a mixture of H2 and NH3 atmospheres. The average diameters of SWNTs are ∼1.5 and ∼3 nm for pure H2 and the H2 and HN3 mixture, respectively. Scanning tunneling spectroscopy (STS) studies show that the SWNTs grown in both atmospheres are doped with nitrogen substituted into the lattice in a pyridine-type structure. This results in a donor feature in the local density of states with an energy that depends on the nitrogen doping concentration.

Boron (B)-alloyed diamondlike carbon (B-DLC) films were prepared on polymethyl methacrylate (PMMA), glass, and silicon (100) using an inductive radio frequency Ar + C2H2 + B2H6 plasma immersion ion processing (PIIP) technique. The composition of the B-DLC films was measured by ion beam analysis techniques, and the bonding structure was characterized by infrared and Raman spectroscopy. The incorporation of B2H6 gas into the PIIP deposition introduced B-C bonds into the DLC structure, resulting in increased sp3-carbon bonding and improved optical performance. The energetic activation of the deposition atoms, induced by the ion bombardment during the PIIP film growth, enhanced the properties of the B-DLC films deposited on dielectric and transparent optical materials. With B-alloying and an optimized deposition energy of 40–135 eV, B-DLC films were synthesized with B-alloying up to 10.4 at.%, high hardness, high refractive index, and optical transmittance that is higher than that of unalloyed DLC films. The experimental results indicate that C-B hybridization and ion-energy transfer are critical to the synthesis of these hard and transparent B-DLC films.

We have studied the preparation of silver-gold alloy nanoparticles based on the phase transfer of metal precursors from aqueous phase to organic solution by a fatty amine at room temperature. Silver-gold nanoparticles were synthesized with different molar ratios (2:1, 1:1, 1:2). Ultraviolet-visible absorption spectra suggested the formation of alloy phases. The elemental Ag:Au ratios in the bimetallic nanoparticles determined by energy dispersive x-ray analysis (EDX) were consistent with the Ag:Au molar ratios used in the feeding solution. Transmission electron microscopy (TEM) revealed the formation of a uniform size distribution of Ag:Au nanoparticles (around 5 nm). X-ray photoelectron spectroscopy (XPS) showed that the composition in the outer part of the Ag:Au nanoparticles was similar to that obtained by EDX analysis, which indicates the formation of homogeneous silver-gold nanoparticles. Silver-gold alloy nanoparticles on a gram scale can be obtained with this method.

Non-destructive investigation of buried interfaces at high-resolution is critical for integrated circuit and advanced packaging research and development. In this letter, we present a novel non-contact microscopy technique using ultrahigh frequency (GHz range) longitudinal acoustic pulses to form images of interfaces and layers buried deep inside a silicon device. This method overcomes fundamental limitations of conventional scanning acoustic microscopy by directly generating and detecting the acoustic waves on the surface of the sample using an ultrafast pump-probe optical technique. We demonstrate our method by imaging copper lines buried beneath a 6-μm silicon wafer; the lateral spatial resolution of 3 μm is limited by the laser spot size. In addition to the high lateral spatial resolution, the technique has picosecond (ps) time resolution and therefore will enable imaging individual interconnect layers in multi-layer stacked devices.

The mechanical properties of biological materials are well adjusted to their function. An excellent example for such materials is the cuticle or exoskeleton of arthropods. In this study, dehydrated cuticle of the American lobster Homarus americanus was examined as a model for a mineralized biological composite material. Nanoindentation testing is a powerful method for revealing gradients and anisotropy in the hardness and the elastic properties of such materials. The air-dried test specimens stem from different parts of the crusher claw with different biological functions. Both the exocuticle and the endocuticle were probed in normal and in the transverse direction to the cuticle surface. For estimating variations in the grade of mineralization, the samples which were tested as cross-sections of the cuticle were analyzed by the use of energy dispersive x-ray mapping. The microstructure of fracture surfaces of the test specimens was investigated using scanning electron microscopy. Due to the use of dehydrated samples, our results do not reflect the exact properties of lobster cuticle in the natural hydrated state, but they can be regarded as a fairly good approximation to the in vivo state.

High-quality lanthanum zirconium oxide (La2Zr2O7 or LZO) films have been deposited and processed on Ni–W substrates using a sol-gel processing approach. It has been demonstrated that crack-free coatings with thicknesses up to 100 nm can be processed in a single step, while thicker coatings (200–225 nm) were processed using a multiple coating and annealing process. Using simulated metalorganic deposition (MOD)-YBa2Cu3O7−δ (YBCO) processing conditions, the barrier properties of the sol-gel LZO coating with a thickness of 120 nm were found to be comparable to that of the standard 3-layer buffer stack deposited using physical vapor deposition. Secondary ion mass spectroscopy depth profile analysis of LZO films annealed in oxygen-18 shows that LZO effectively stops the diffusion of Ni within the first 80–100 nm. Using MOD processes, a CeO2 cap layer and superconducting YBCO layer were deposited on sol-gel LZO/Ni–W. For the first time, using such an all-solution conductor architecture, a critical current (Ic) of 140 A/cm with a corresponding critical current density (Jc) of 1.75 MA/cm2 has been demonstrated. Using a very thin Y2O3 seed layer (∼10 nm) deposited by electron beam evaporation; improved texture quality in the LZO layers has been demonstrated. The performance of the LZO deposited on these samples was evaluated using a sputtered CeO2 cap layer and MOD YBCO layer. Critical currents of up to 255 A/cm (3.2 MA/cm2) with 0.8-μm-thick YBCO films have been demonstrated, comparable to the performance of films grown using physical vapor deposited yttria stabilized zirconia as a barrier layer. Similar experiments using an MOD-CeO2 cap layer and MOD-YBCO layer yielded critical currents of 200 A/cm (2.5 MA/cm2) with 0.8-μm-thick YBCO films.

Sn–In alloys are promising low-melting-point Pb-free solders. Cu and Ni are common substrates in the electronic products. This study examines the interfacial reactions in the Sn–20 at.% In(γ–InSn4)/Cu and Sn–20 at.% In/Ni couples at 160 °C. Only the η–Cu6Sn5 phase layer is formed in the Sn–20 at.% In/Cu couple, and the layer grows thicker with longer reaction time. The reaction path is γ–InSn4/η–Cu6Sn5/Cu. A peculiar phenomenon with the bulging of the couple near the Ni substrate is found in the Sn–20 at.% In/Ni couple. A liquid phase is formed by interfacial reaction in the solid/solid Sn–20 at.% In/Ni couple at 160 °C, and the reaction path is γ–InSn4/liquid/δ–Ni3Sn4 + liquid/(δ–Ni3Sn4)/Ni. Usually Ni has a slower reaction rate with solders; however, the consumption rates of Ni substrate are much higher than those of Cu substrate in this study when they are in contact with the Sn–20 at.% In alloy at 160 °C due to the formation of the liquid phase in the Sn–20 at.% In/Ni couple.

Here we demonstrate the synthesis of a new type of layered poly(3,4-ethylenedioxy- thiophene) (PEDOT)/MoS2 nanocomposite via flocculation of delaminated MoS2 with subsequent in situ oxidative polymerization of 3,4-ethylenedioxythiophene. The resulting nanocomposite was characterized by Fourier transform infrared spectroscopy, powder x-ray diffraction, x-ray photoelectron spectroscopy, thermal analysis, transmission electron microscopy, and four-probe electrical conductivity measurements with respect to temperature. X-ray diffraction results indicated that the exfoliated MoS2 and PEDOT are restacked to produce a novel nanoscale composite material containing alternate nanoribbons of PEDOT in between MoS2 with a basal distance of ∼1.38 nm. The nanocomposite, which could be used as a cathode material for small power rechargeable lithium batteries, has also been demonstrated by the electrochemical insertion of lithium into the PEDOT/MoS2 nanocomposite, where a significant enhancement in the discharge capacity is observed, compared to that of respective pristine molybdenum disulfide.

The molecular dynamics method has been used to simulate mode I cracking in body-centered-cubic iron. Close attention has been paid to the process of the atomic configuration evolution of the cracks. The simulation shows that at low temperatures, partial dislocations are emitted before the initiation of crack propagation, subsequently forming the stacking faults or multilayer twins on {112} planes, and then brittle cleavage and extended dislocation nucleation are observed at the crack tip accompanied by twin extension. These results are in agreement with the experimental observation that twinning and fracture processes cooperate at low temperatures. Furthermore, an energetics analysis has been made on the deformation behavior observed at the crack tip. The effect of temperature on the fracture process is discussed. At the higher temperature, plastic deformation becomes easier, and crack blunting occurs. With increasing temperature, the fracture resistance increases, and the effect of the lattice trapping can be weakened by thermal activation.

In this study, we demonstrated that the failure of bulk metallic glasses (BMGs) results from a sudden temperature rise within a shear band. Using a shear transformation zone model, we successfully calculated the temperature within a shear band and found it consistent with the observation from an in situ infrared thermographic system. The instantaneous temperature within a shear band at fracture agrees remarkably well with the glass transition temperature (Tg providing a new criterion to determine the strength of BMGs from their Tg. This agreement also discloses the fact that catastrophic failure of BMG is caused by the sudden drop in viscosity inside the shear band when the instantaneous temperature within a shear band approaches Tg.

Acquired salivary pellicle is a thin protein-rich film formed by the adsorption of saliva onto teeth. It plays important roles in lubrication during mastication and protecting the teeth from chemical attack. Pellicle can become colonized by bacteria to form dental plaque which can lead to dental caries if the bacteria are acidogenic. Abrasive polishing with a dentrifice is used periodically to remove the pellicle from teeth. Pellicle can interact with dietary polyphenolic compounds (tannins) to create extrinsic stains on the tooth surface. The staining can modify the pellicle's mechanical properties and change its morphology resulting in a “squeaky” feeling when the tongue is rubbed over the teeth. Atomic force microscopy imaging and nanoscale mechanical measurements show that unstained pellicle has a dense undulating morphology and is a surprisingly stiff, viscoelastic solid. In contrast, tannin-stained pellicle has fewer but larger surface undulations and exhibits substantial viscous creep.

HfB2–15 vol% MoSi2 composites were produced from powder mixtures and densified through different techniques, namely hot pressing and spark plasma sintering. Dense materials were obtained at 1900 °C by hot pressing and at 1750 °C by spark plasma sintering. Microstructure and mechanical properties were compared. The most relevant result was for high-temperature strength: independent of the processing technique, the flexural strength in air at 1500 °C was higher than 500 MPa.

Measurements of vibrational spectra of atomic force microscopy (AFM) microprobes in contact with a sample allow a good correlation between resonance frequencies shifts and the effective elastic modulus of the tip-sample system. In this work we use finite element methods for modeling the AFM microprobe vibration considering actual features of the cantilever geometry. This allowed us to predict the behavior of the cantilevers in contact with any sample for a wide range of effective tip-sample stiffness. Experimental spectra for glass and chromium were well reproduced for the numerical model, and stiffness values were obtained. We present a method to correlate the experimental resonance spectrum to the effective stiffness using realistic geometry of the cantilever to numerically model the vibration of the cantilever in contact with a sample surface. Thus, supported in a reliable finite element method (FEM) model, atomic force acoustic microscopy can be a quantitative technique for elastic-modulus measurements. Considering the possibility of tip-apex wear during atomic force acoustic microscopy measurements, it is necessary to perform a calibration procedure to obtain the tip-sample contact areas before and after each measurement.

Single-walled carbon nanotubes (SWNTs) have been used as electrocatalyst support for fuel cells. A toluene solution of a platinum salt, bis(dibenzylideneacetone) platinum, has been used for the first time to decorate the outer surface of SWNT bundles with Pt nanoparticles. The obtained Pt/SWNT materials were then used as catalytic layer in electrodes for fuel cell electrocatalysis. The used platinum salt concentration in the initial SWNT dispersion determined the Pt nanoparticle size and, consequently, the activity of the Pt/SWNT electrodes toward the oxygen reduction reaction. The achieved results were compared with those corresponding to a commercial Pt/carbon black catalyst with similar Pt loading and surface area.

Polyamide 66 (PA66) nanotubes with an array structure were prepared by infiltrating a solution of normal molecular weight PA66 into anodic aluminum oxide (AAO) templates with a pore diameter of 200 nm. The results of field-emission scanning electron microscopy (FESEM) demonstrate that PA66 nanotubes with a wall thickness of about 60 nm can be fabricated by a solution-wetting method and PA66 nanotubes and nanowires can be obtained by a melt-wetting method at different temperature. We also find that PA66 nanotubes have the “super plasticity” for the crystalline belts in their wall may arrange by spiraling and rounding style. Thermogravimetric analysis (TGA) indicates the nanotubes have a better thermal stability than bulk polymer PA66. The mechanism of forming polymer nanotubes by polymer melt-wetting method has been proposed.

Layered manganese oxide nanocomposite (PQN2MO) with Polyquaternium-2 (PQN2) incorporated between manganese oxide sheets was synthesized through a delamination/reassembling process. The synthesized material was characterized by powder x-ray diffraction (XRD), elemental analysis, thermal analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy observation. XRD analysis showed that the expansion of the interlayer depended on the amount of PQN2 intercalated; the largest expansion was 0.94 nm, corresponding to a layer of PQN2 chains existing in the interlayer at an angle of about 30°. Chemical analysis results indicated that the tetramethylammonium (TMA+) ions in the interlayer were partly replaced by PQN2 polycations by an ion exchange mechanism, resulting in a nanocomposite in which TMA+ ions and PQN2 polycations simultaneously existed in the interlayer. The intercalated PQN2 polycations were selectively extracted, and TMA+ ions were stable enough to remain in the interlayer against the acid treatment. PQN2MO nanocomposite was composed of platelike nanocomposite particles.

Tantalum zirconium oxynitrides in the Ta–Zr–O–N system of Ta(3−x)Zrx(O/N)6 and Ta(3−x)ZrxN(5−x)Ox (0 ≤ x ≤ 0.6) compositions have been synthesized by the nitridation of the amorphous tantalum zirconium oxides, obtained by sol-gel technique, with flowing ammonia at temperatures in the range 1023–1123 K for several hours. Different coloration has been obtained, going from yellow to red, whose intensity is a function of the nitrogen content in each sample. The structure of these oxynitrides has been refined from powder x-ray diffraction by the Rietveld method. The present study shows that the baddeleyite phase is formed in the preliminary stages of the nitridation and then transformed to the Ta3N5-type phase. Below 1123 K, a baddeleyite-type structure with a monoclinic symmetry, space group P21/c, is observed in these phases. When the nitration temperature increases, a marked increase in the nitrogen content takes place, and these materials adopt the Ta3N5 structure, space group C2/m. Diffuse reflectance spectra and CIE-LAB color coordinates suggest that the solid solutions Ta(3−x)Zrx(O/N)6 and Ta(3−x)ZrxN(5−x)Ox (0 ≤ x ≤ 0.6) are expected to be promising candidates for new ecological pigments.

In this paper, we report a facile route, the tin vapor treatment method, to prepare tin oxide containing mesoporous silica composites (TOMS), which display room-temperature photoluminescence (RT-PL). Among them, TOMS-1 and TOMS-2 were synthesized from mesoporous silica SBA-15 and KIT-6, respectively. They are composed of amorphous SiO2 and tin oxide species and they display strong emission near ultraviolet (UV) when excited by UV light. By increasing the preparation temperature, their Sn content can be increased and subsequently their photoluminescence (PL) intensities can be greatly enhanced. Besides, their PL properties are revealed to be closely related to 2-fold-coordinated tin oxygen-deficient centers.

The phase evolution of magnesium incorporated hydroxyapatite/β-tricalcium phosphate (HA/β-TCP) ceramics of high purity prepared by solid-state reaction was investigated with the aid of x-ray diffraction and infrared spectroscopy (IR) in transmittance mode analysis. The dependence of the microstructure on the phase evolution of biphasic ceramics during natural sintering was also investigated as a function of Mg content. When sintered at 1100 °C, Mg is preferentially incorporated into the β-TCP phase rather than the HA phase. This Mg incorporation into the β-TCP effectively suppresses the phase transition from β- to α-TCP. With increasing sintering temperature, the solubility limit of the Mg in the β-TCP decreases and Mg starts to be either incorporated into the HA phase or segregated as free MgO. The decreased Mg content in the β-TCP facilitates the phase transition from β- into α-TCP, at 1300 °C or higher. Different processing methods on Mg addition show that the retarded phase transition from β- to α-TCP is the inherent property of Mg-doped HA/TCP. The variations in processing parameters mainly affect the microstructure instead of the phase evolution, leading to highly densified HA/β-TCP ceramics.