The dynamic mechanical behaviour of a series of cyclic olefin copolymers (COCs) with varying norbornene content has been examined in the vicinity of the glass transition temperature, Tg. The temperature of the transition has been shown to increase linearly with increase in norbornene content. Measurements of both the elastic storage modulus, E′, and loss modulus, E″, have decreased exponentially with rise in temperature above Tg . A levelling-off in E″ occurred at >20 °C above Tg for all copolymers. The results of Dynamic Mechanical Thermal Analysis (DMTA) have been used in the identification of optimum conditions for hot embossing. At >20 °C above Tg in a region of viscous liquid flow, the hot embossing of COC has resulted in a full replication of channel depth without cracking or distortion.

The synthesis, mechanical and magnetic properties of bulk composite Fe72B19.2Si4.8M4 (M=Cr, Zr) alloys obtained by a copper mould injection casting technique under a protective helium atmosphere are reported and discussed. The resultant microstructure of the composite alloys consists of crystalline Fe92Si8 and Fe2B phases embedded in a glassy matrix. The values of microhardness (Hv ) show maxima for the alloy containing Cr with 10.24±0.95 GPa. The maximum value of saturation magnetization average (μ0 Ms ) is 1.25±0.02 T for Cr-containing alloy. The Curie temperatures (Tc ) of amorphous phases are higher than 390 K for both alloys. However, the bulk composite alloys presents values for crystallization temperature (Tx ) of 1289±10 K and 1140±10 K for Cr and Zr-containing alloys, respectively. These results are interpreted on the basis of the interplay between the crystalline and amorphous phases.

Nanoporous Anodic Alumina Films (NAAF) have been used for growing a lot of nanostructure functional materials. Of particular interest is the NAAF conversion into membranes (NAAM) with different highly controlled pore diameter and distribution to be used as templates and masks to grow a wide variety of nanomaterials. This work constitutes an approach to a review of our latest results regarding the use of NAAF and NAAM as templates in which II-VI semiconductor, functional oxides, hard materials and magnetic nanowires have been grown. The growth techniques and methods used include Isothermal Close Space Sublimation (ICSS), Magnetron Sputtering, electroplating and sol-gel. Ion Beam Irradiation (IBI) combined with different NAAM as masks has been also used for Titania substrates functionalization.

Fabrication of transparent, conductive phase-segregated ITO/PC composites was accomplished by compression molding of dry mixed constituents. Mixtures of 50nm indium tin oxide particles in a polycarbonate matrix of compositions ranging from phr = 1.0 to 0.001 were measured by optical and electrical methods. Measured transmittance ranged from 5% to 68% at 400nm, 15% to 80% at 700nm, and averaged 10% to 75% across the visible spectrum. Resistance was measured by impedance spectroscopy. Resistivities of the different composites spanned 10 orders of magnitude. Electrical percolation was found to occur near phr = 0.15.

Microelectromechanical Systems (MEMS) market is a rapidly growing market with a wide range of devices. Most of these devices require an interaction with an electronic circuit, and with the increasing number of high performance MEMS devices that are being introduced, a demand for integrating CMOS and MEMS using high-density and low-parasitic interconnects have also been on the rise.

Unfortunately, conventional methods of integrating CMOS with MEMS cannot provide the high density and low-parasitic interconnections required by modern high performance MEMS devices, and at the same time provide the flexibility required to accommodate new devices that are made using new materials and highly innovative fabrication processes.

Heterogeneous 3D integration of MEMS and CMOS has the potential to provide both the performance and the integration flexibility; however there are two interconnect challenges that need to be addressed. This paper outlines the details of these interconnect challenges and introduces two interconnect technologies, Mechanically Flexible Interconnects (MFI) and Through-Silicon Via (TSV), developed specifically to address these challenges.

To shed light on the nature of the electronic states at play in N-doped TiO2 nanoparticles, we have performed detailed ground and excited state calculations on pure and N-doped TiO2 rutile using an embedding model. We have validated our model by comparing ground-state embedded results with those obtained from periodic DFT calculations. Our results are consistent with periodic calculations. Using this embedding model we have performed B3LYP based TDDFT calculations of the excited state spectrum. We have also studied the lowest excitations using high-level equation-of-motion coupled cluster (EOMCC) approaches involving all single and inter-band double excitations. We compare and contrast the nature of the excitations in detail for the pure and doped systems using these calculations. Our calculations indicate a lowering of the bandgap and confirm the role of the N3- states on the UV/Vis spectrum of N-doped TiO2 rutile supported by experimental findings.

Design of semiconducting nanomaterials with an indirect electronic bandgap is currently one of the major areas of research to obtain a high thermoelectric yield by lowering their lattice thermal conductivity. Intensive investigations on superlattices were performed to achieve this goal. However, like one-dimensional nanowires, they decrease heat transport in only one propagation direction of the phonons. Moreover, they often lead to dislocations since they are composed of layered materials with a lattice mismatch. Design of superlattices with a thermoelectric figure of merit ZT higher than unity is therefore hazardous. Self-assembly of epitaxial layers on silicon has been used for bottom-up synthesis of three-dimensional (3D) Ge quantum-dot (QD) arrays in Si for quantum-device and solar-energy applications. Using the atomic-scale 3D phononic crystal model, it is predicted that high-density 3D arrays of self-assembled Ge QDs in Si can as well show an extreme reduction of the thermal transport. 3D supercrystals of Ge QDs in Si present a thermal conductivity that can be as tiny as that of air. These extremely low values of the thermal conductivity are computed for a number of Ge filling ratios and size parameters of the 3D Si-Ge supercrystal. Owing to incoherent phonon scattering with predominant near-field effects, the same conclusion holds for supercrystals with moderate QD disordering. As a result, design of highly-efficient CMOS-compatible thermoelectric devices with ZT possibly much higher than unity might be possible. In this theoretical study, simultaneous evolution of both temperature and average distance between the Ge QDs is analyzed for a non-variable Ge filling ratio to obtain thermal-conductivity values as low as that of air (+/- 0.025 W/m/K).

The visible photoluminescence of nanocrystalline TiO2 is examined in the presence of surface binding agents and as a function of vacuum annealing in order to probe the molecular nature of surface defects. The photoluminesence (PL) of bulk crystals of anatase TiO2 from (101) and (001) planes is also reported in order to test the hypothesis that electron and hole traps are spatially isolated on different crystal planes. We find that a number of hole scavengers are capable of quenching the PL associated with trapped electrons, while the ability of oxygen to quench PL through electron scavenging varies with the nature of the sample. We conclude that hole scavengers exert their influence on the PL through reaction with valence band holes rather than with spatially isolated trapped holes. Scavenging of electrons by O2, on the other hand, depends on adsorption at oxygen vacancies and varies with TiO2 sample.

Mg2Si1-xRx (R-Sb,Bi) compositions with x=0.025, 0.05 for Sb and x=0.01,0.025, 0.05 for Bi were synthesized by induction melting of the constituent elements followed by compaction by hot pressing. Phase identification by x-ray diffraction (XRD) indicate a biphasic nature for Bi substituted compositions for x≥.025 while solid solubility for the different Sb substitutions. Abundance distribution plots of the Seebeck (S) coefficient show asymmetry in the Sb compositions and is not observed in the Bi substituted samples. This indicates presence of vacancies only in the Sb substituted compositions. Electrical conductivity (σ), Seebeck coefficient (S) and thermal conductivity (κ) values were measured from 300K to 773 K. The observed trends in the absolute values of α and S can be explained based on doping/second phase influence in Bi substitutions and due to effect of vacancies for Sb substitutions. The (κL) (phonon component) values show a significant decrease for the Sb substitutions due to the presence of vacancies. Calculation of the thermoelectric figure of merit (ZT) show a ZTmax of 0.56 for x=0.025 Bi composition compared to a ZTmax of ∼ 0.05 for Mg2Si.

The ζ-phase, existing between 35 and 70% U in Pu, belongs to the high density phases seen from the point of view of systematics of allotropic modifications of Pu metal. Despite the volume per actinide atom only slightly higher than for α-Pu, it magnetic susceptibility is much higher than for α-Pu and exceeds even the δ-Pu value. Similarly, the Sommerfeld coefficient γ > 40 mJ/mol Pu K2 exceeds the experimental δ-Pu value. The data confirm that the volume is not the primary control parameter affecting the situation around the Fermi level of common Pu phases and they point against the traditional belief that they are essentially narrow 5f band systems.

Using Molecular Dynamics we study the role of electronic excitations in the radiation damage caused by an energetic ion in Ge nanocrystals embedded in amorphous SiO2. The electronic effects are included as heating along the ion path modeled by the thermal spike model. In an ion energy regime where the electronic stopping power is larger than the nuclear, we find that the electronic effects enhance the defect creation significantly. We conclude that the electronic excitations below the track production threshold due to an energetic ion cannot be disregarded as a source of radiation damage.

Zr0.5Hf0.5Ni0.8Pd0.2Sn0.99Sb0.01 composites with various concentrations of WO3 inclusions were synthesized by mechanical alloying using high energy shaker mill. High density hot pressed pellets of the synthesized materials were characterized using powder X-ray diffraction and transmission electron microscopy and their thermoelectric properties were investigated in the temperature range from 300 to 750 K. The electrical conductivity of the composites at 300 K decreases from 2500 S/cm for 0 wt.% WO3 alloy to 2200 S/cm for the composite with 2 wt.% WO3 inclusion. The electrical conductivity of composites containing 5 wt.% and 10 wt.% WO3 inclusions showed sharp increases with increasing WO3 content. The electrical conductivity of the composites monotonically decreases with rising temperature. All samples showed n-type semiconducting behavior and the thermopower values decrease with increasing WO3 content. The lattice thermal conductivity of the composites increases with increasing WO3 content. However, these values are about 30% lower than that of Zr0.5Hf0.5Ni0.8Pd0.2Sn0.99Sb0.01 alloy prepared by high temperature solid-state techniques. The synthesized composites showed lower figure of merit than the half-Heusler matrix due to large reduction in the thermopower values with increasing WO3 content.

We have employed a simple and novel solution processing method to prepare V2O5-WO3 composite films which demonstrate enhanced Li-ion intercalation properties for applications in lithium-ion batteries. It should be noted that this solution processing method employs precursors that only contain the elements of V, W, O and H, which avoids impurity elements such as Na that has been commonly used in other solution methods. The V2O5-WO3 composite films show enhanced Li-ion intercalation properties compared to pure V2O5 and WO3 films. For example, V2O5-WO3 film with a molar ratio V2O5/WO3 of 10/1 exhibits a discharge capacity of 254 mA•h/g, while the pure V2O5 film delivers a discharge capacity of 76 mA•h/g at a high current density of 1.33 A/g. Such enhanced Li-ion intercalation properties are attributed to the reduced crystallinity and increased porosity and surface area in the composite films. In addition, the chronopotentiometric curves of the V2O5-WO3 film with a mol ratio of 10:1 are distinctively different from those of pure oxide films and other composite films with different V2O5/WO3 mol ratios, suggesting a different Li-ion intercalation process in the V2O5-WO3 film with the mol ratio of 10/1.

In the last 40 years, the increased space activity created a new form of space environment of hypervelocity objects—space debris—that have no functional use. The space debris, together with naturally occurring ultrahigh velocity meteoroids, presents a significant hazard to spacecraft. Collision with space debris or meteoroids might result in disfunction of external units such as solar cells, affecting materials properties, contaminating optical devices, or destroying satellites. The collision normally results in the formation of additional debris, increasing the hazard for future missions. The hypervelocity debris effect is studied by retrieving materials from space or by using ground simulation facilities. Simulation facilities, which include the light gas gun and Laser Driven Flyer methods, are used for studying the materials degradation due to debris impact. The impact effect could be accelerated when occurring simultaneously with other space environment components, such as atomic oxygen, ultraviolet, or x-ray radiation. Understanding the degradation mechanism might help in developing materials that will withstand the increasing hazard from the space debris, allowing for longer space missions. The large increase in space debris population and the associated risk to space activity requires significant measures to mitigate this hazard. Most current efforts are being devoted to prevention of collisions by keeping track of the larger debris and avoiding formation of new debris.

SiOx nanowires can be grown via the vapor-liquid-solid growth mechanism using SiO vapor produced during the active oxidation of a Si substrate. The as-grown SiOx nanowire have a range of useful physical properties but can also be used as large surface area substrates for the growth of secondary materials. In this study we report the use of optically active impurities to grow and dope secondary nanowire structures, and the use of simple coating methods to enhance and extend the functionality of these unique nanowire substrates.

The influence of incorporating nanoparticulate additions into Ca3Co4O9 (CCO) thin films prepared by pulsed laser deposition using composite targets of CCO and CCO + 3wt% BaZrO3 (BZO) on Si and LaAlO3 substrates is investigated. X-ray data and high-resolution scanning electron microscopy reveal preferred c-axis orientation of the films deposited on Si substrates with the formation of nanoparticles between ∼ 10 – 50 nm. Preliminary thermoelectric behavior shows an enhancement of the power factor α2/ρ at room temperature. The microstructure and thermoelectric behavior of the CCO films are compared to the BZO-doped films.

The Joule heating effect at various stages under electromigration of flip-chip Sn3.5Ag solder joints was investigated under a current of 0.5 A at 100°C. During various stages of electromigration, voids may form and propagate and Joule heating effect may vary at different void sizes. To verify the void nucleation and propagation on Joule heating effect during electromigration process, the solder bump was stressed for different lengths of time and then examined by Kelvin bump probes and infrared microscopy. We found that voids started to form at approximately 1.2 times of the initial bump resistance. Then the voids propagated when the bump resistance increased. In addition, the temperature of the solder joints increased with the bump resistance and the increase of current stressing time. It increased very slowly in initial stages. In the last stage, the temperature of the solder bump increased rapidly due to the increase of the bump resistance and the local Joule heating effect.

Photo-induced electron transfer and recombination was investigated for prototype molecular absorbers covalently bound to metal-oxide films. Two perylene derivatives with different anchor/bridge groups, a propionic and an acrylic acid, were adsorbed on both bare ZnO nanorods and TiO2 coated nanorods and the dynamics of the systems compared.

We have prepared a variety of filled skutterudites through non-equilibrium synthesis by converting melt-spun ribbons into single phase polycrystalline bulk under pressure. In general, better thermoelectric properties are found in these samples. In this work, we performed microstructure characterization of non-equilibrium synthesized p-type filled skutterudite CeFe4Sb12 by X-ray diffraction, scanning electron microscopy and transmission electron microscopy in order to understand the structural origin of the improved thermoelectric properties. It is found that the non-equilibrium synthesized samples have smaller grain size and cleaner grain boundaries when compared to the samples prepared by the conventional solid-state reaction plus long term annealing. While smaller grain size can help reduce the lattice thermal conductivity, cleaner grain boundaries ensure higher carrier mobility and subsequently, higher electrical conductivity at the application temperatures.

Two lanthanide borosilicate (LaBS) glasses containing 9.5 and 5.0 wt.% PuO2 prepared at 1500 °C consisted of a vitreous phase and minor crystalline PuO2 (or PuO2-HfO2 solid solution with minor HfO2) and britholite-type phases. X-ray absorption spectra of Pu LIII edge in the as-prepared and stored for various periods LaBS glasses were recorded, analyzed and compared with the spectra of crystalline PuO2. Pu in the as-prepared glass existed in predominantly tetravalent form (Pu4+ ions) but its storage in air results in partial oxidation as was seen from shift of peak energy values. In the structure of the as-prepared glass, Pu4+ ions had a co-ordination number (CN) close to 6 (˜6.3) and were located within the axially squeezed octahedra with five equidistant oxygen ions at a distance of 2.265±0.015 Å and one – at shorter distance (2.130±0.010 Å) from the Pu4+ ion. The Pu—Pu(M) distance (second co-ordination shell) was 3.675±0.015 Å. “Aging” of the LaBS glass with transformation of some fraction of Pu into penta- or/and hexavalent form was accompanied by a structural transformation.