Size effects on tensile and fatigue behaviour of polycrystalline metal foils at the micrometer scale

Tensile and fatigue properties of as-rolled and annealed polycrystalline Cu foils with different thicknesses at the micrometer scale were investigated. Uniaxial tensile testing results showed that with decreasing foil thickness the uniform elongation decreases for both as-rolled and annealed foils, whereas the yield strength and ultimate tensile strength increase for as-rolled foils, but decrease for the annealed foils. For both the as-rolled or annealed foils, bending fatigue resistance decreases with decreasing the foil thickness. Deformation and fatigue damage behaviour of the free-standing foils were characterised as a function of foil thickness. In addition, the fatigue strength of various small-scale Cu foils was compared to understand they physical mechanisms of size effects on mechanical properties of the metallic material at micrometer scales.

Performance characterization of VGCF/epoxy nanocomposite sensors under static load cycles and in static structural health monitoring

Compared to conventional metal-foil strain gauges, nanocomposite piezoresistive strain sensors have demonstrated high strain sensitivity and have been attracting increasing attention in recent years. To fulfil their ultimate success, the performance of vapor growth carbon fiber (VGCF)/epoxy nanocomposite strain sensors subjected to static cyclic loads was evaluated in this work. A strain-equivalent quantity (resistance change ratio) in cantilever beams with intentionally induced notches in bending was evaluated using the conventional metal-foil strain gauges and the VGCF/epoxy nanocomposite sensors. Compared to the metal-foil strain gauges, the nanocomposite sensors are much more sensitive to even slight structural damage. Therefore, it was confirmed that the signal stability, reproducibility, and durability of these nanocomposite sensors are very promising, leading to the present endeavor to apply them for static structural health monitoring.

A nanometre-scale non-periodic structural variation in high temperature superconducting ceramics and the implications for properties

Non-periodic structural variation has been found in the high Tc cuprates, YBa2Cu3O7-x and Hg0.67Pb0.33Ba2Ca2Cu 3O8+δ, by image analysis of high resolution transmission electron microscope (HRTEM) images. We use two methods for analysis of the HRTEM images. The first method is a means for measuring the bending of lattice fringes at twin planes. The second method is a low-pass filter technique which enhances information contained by diffuse-scattered electrons and reveals what appears to be an interference effect between domains of differing lattice parameter in the top and bottom of the thin foil. We believe that these methods of image analysis could be usefully applied to the many thousands of HRTEM images that have been collected by other workers in the high temperature superconductor field. This work provides direct structural evidence for phase separation in high Tc cuprates, and gives support to recent stripes models that have been proposed to explain various angle resolved photoelectron spectroscopy and nuclear magnetic resonance data. We believe that the structural variation is a response to an opening of an electronic solubility gap where holes are not uniformly distributed in the material but are confined to metallic stripes. Optimum doping may occur as a consequence of the diffuse boundaries between stripes which arise from spinodal decomposition. Theoretical ideas about the high Tc cuprates which treat the cuprates as homogeneous may need to be modified in order to take account of this type of structural variation.

Ultrasensitive strain sensors made from metal-coated carbon nanofiller/epoxy composites

A set of resistance-type strain sensors has been fabricated from metal-coated carbon nanofiller (CNF)/epoxy composites. Two nanofillers, i.e., multi-walled carbon nanotubes and vapor growth carbon fibers (VGCFs) with nickel, copper and silver coatings were used. The ultrahigh strain sensitivity was observed in these novel sensors as compared to the sensors made from the CNFs without metal-coating, and conventional strain gauges. In terms of gauge factor, the sensor made of VGCFs with silver coating is estimated to be 155, which is around 80 times higher than that in a metal-foil strain gauge. The possible mechanism responsible for the high sensitivity and its dependence with the networks of the CNFs with and without metal-coating and the geometries of the CNFs were thoroughly investigated.

Reactive oxygen plasma-enabled synthesis of nanostructured CdO : tailoring nanostructures through plasma–surface interactions

Plasma-assisted synthesis of nanostructures is one of the most precise and effective approaches used in nanodevice fabrication. Here we report on the innovative approach of synthesizing nanostructured cadmium oxide films on Cd substrates using a reactive oxygen plasma-based process. Under certain conditions, the surface morphology features arrays of crystalline CdO nano/micropyramids. These nanostructures grow via unconventional plasma-assisted oxidation of a cadmium foil exposed to inductively coupled plasmas with a narrow range of process parameters. The growth of the CdO pyramidal nanostructures takes place in the solid-liquid-solid phase, with the rates determined by the interaction of plasma-produced oxygen atoms and ions with the surface. It is shown that the size of the pyramidal structures can be effectively controlled by the fluxes of oxygen atoms and ions impinging on the cadmium surface. The unique role of the reactive plasma environment in the controlled synthesis of CdO nanopyramidal structures is discussed as well.

Anodized nanoporous WO3 Schottky contact structure for hydrogen and ethanol sensing

This paper reports the development of nanoporous tungsten trioxide (WO3) Schottky diode-based gas sensors. Nanoporous WO3 films were prepared by anodic oxidation of tungsten foil in ethylene glycol mixed with ammonium fluoride and a small amount of water. Anodization resulted in highly ordered WO3 films with a large surface-to-volume ratio. Utilizing these nanoporous structures, Schottky diode-based gas sensors were developed by depositing a platinum (Pt) catalytic contact and tested towards hydrogen gas and ethanol vapour. Analysis of the current–voltage characteristics and dynamic responses of the sensors indicated that these devices exhibited a larger voltage shift in the presence of hydrogen gas compared to ethanol vapour at an optimum operating temperature of 200 °C. The gas sensing mechanism was discussed, associating the response to the intercalating H+ species that are generated as a result of hydrogen and ethanol molecule breakdowns onto the Pt/WO3 contact and their spill over into nanoporous WO3.

Substrate effects in the supramolecular assembly of 1,3,5-benzene tricarboxylic acid on graphite and graphene

The behavior of small molecules on a surface depends critically on both molecule–substrate and intermolecular interactions. We present here a detailed comparative investigation of 1,3,5-benzene tricarboxylic acid (trimesic acid, TMA) on two different surfaces: highly oriented pyrolytic graphite (HOPG) and single-layer graphene (SLG) grown on a polycrystalline Cu foil. On the basis of high-resolution scanning tunnelling microscopy (STM) images, we show that the epitaxy matrix for the hexagonal TMA chicken wire phase is identical on these two surfaces, and, using density functional theory (DFT) with a non-local van der Waals correlation contribution, we identify the most energetically favorable adsorption geometries. Simulated STM images based on these calculations suggest that the TMA lattice can stably adsorb on sites other than those identified to maximize binding interactions with the substrate. This is consistent with our net energy calculations that suggest that intermolecular interactions (TMA–TMA dimer bonding) are dominant over TMA–substrate interactions in stabilizing the system. STM images demonstrate the robustness of the TMA films on SLG, where the molecular network extends across the variable topography of the SLG substrates and remains intact after rinsing and drying the films. These results help to elucidate molecular behavior on SLG and suggest significant similarities between adsorption on HOPG and SLG.

Pre-lithiation of onion-like carbon/MoS2 nano-urchin anodes for high-performance rechargeable lithium ion batteries

Hybrid urchin-like nanostructures composed of a spherical onion-like carbon (OLC) core and MoS2 nanoleaves were synthesized by a simple solvothermal method followed by thermal annealing treatment. Compared to commercial MoS2 powder, MoS2/OLC nanocomposites exhibit enhanced electrochemical performance as anode materials of lithium-ion batteries (LIBs) with a specific capacity of 853 mA h g−1 at a current density of 50 mA g−1 after 60 cycles, and a moderate initial coulombic efficiency of 71.1%. Furthermore, a simple pre-lithiation method based on direct contact of lithium foil with MoS2/OLC nano-urchins was used to achieve a very high coulombic efficiency of 97.6% in the first discharge/charge cycle, which is at least 26% higher compared to that of pristine MoS2/OLC nano-urchins. This pre-lithiation method can be generalized to develop other carbon-metal sulfide nanohybrids for LIB anode materials. These results may open up a new avenue for the development of the next-generation high-performance LIBs.

General properties of electrochemical capacitors

The use of capacitors for electrical energy storage actually predates the invention of the battery. Alessandro Volta is attributed with the invention of the battery in 1800, where he first describes a battery as an assembly of plates of two different materials (such as copper and zinc) placed in an alternating stack and separated by paper soaked in brine or vinegar [1]. Accordingly, this device was referred to as Volta’s pile and formed the basis of subsequent revolutionary research and discoveries on the chemical origin of electricity. Before the advent of Volta’s pile, however, eighteenth century researchers relied on the use of Leyden jars as a source of electrical energy. Built in the mid-1700s at the University of Leyden in Holland, a Leyden jar is an early capacitor consisting of a glass jar coated inside and outside with a thin layer of silver foil [2, 3]. With the outer foil being grounded, the inner foil could be charged with an electrostatic generator, or a source of static electricity, and could produce a strong electrical discharge from a small and comparatively simple device.

Effect of Packaging Materials and Storage on Major Volatile Compounds in Three Australian Native Herbs

Lemon myrtle, anise myrtle, and Tasmanian pepper leaf are commercial Australian native herbs with a high volatile or essential oil content. Packaging of the herbs in high- or low-density polyethylene (HDPE and LDPE) has proven to be ineffective in preventing a significant loss of volatile components on storage. This study investigates and compares the effectiveness of alternate high-barrier property packaging materials, namely, polyvinylidene chloride coated polyethylene terephthalate/casted polypropylene (PVDC coated PET/CPP) and polyethylene terephthalate/polyethylene terephthalate/aluminum foil/linear low-density polyethylene (PET/PET/Foil/LLDPE), in prevention of volatile compound loss from the three native herbs stored at ambient temperature for 6 months. Concentrations of major volatiles were monitored using gas chromatography?mass spectrometry (GC-MS) techniques. After 6 months of storage, the greatest loss of volatiles from lemon myrtle was observed in traditional LDPE packaging (87% loss) followed by storage in PVDC coated PET/CPP (58% loss) and PET/PET/Foil/LLDPE (loss of 23%). The volatile loss from anise myrtle and Tasmanian pepper leaf stored in PVDC coated PET/CPP and PET/PET/Foil/LLDPE packaging was <30%. This study clearly indicates the importance of selecting the correct packaging material to retain the quality of herbs with high volatile content.

Schiff Base Complexes and their Assemblies on Surfaces

Schiff bases and their transition metal complexes are of significant current interest even though they have been prepared for decades. They have been used in various applications such as catalysis, corrosion protection, and molecular sensors. In this study, N-aryl Schiff base ketimine ligands as well as numerous new, differently substituted salen and salophen-type ligands and their cobalt(II), copper(II), iron(II), manganese(II), and nickel(II) complexes were synthesised. New solid state structures of the above compounds and the dioxygen coordination properties of cobalt(II) complexes and catalytic properties of three synthesised binuclear complexes were examined. The prepared complexes were applied in the formation of self-assembled layers on a polycrystalline gold surface and liquid-graphite interface. The effect of metal ion and ligand structure on the as-formed patterns was studied. When studying gold surfaces, a unique thiol-assisted dissolution of elemental gold was observed and a new thin gold foil preparation method was introduced. In the summary, synthesis, structures, and properties of Schiff base ligands and their transition metal complexes are described in detail and the applications of these reviewed. Assemblies of other complexes on a liquid-graphite interface and on a gold surface are also presented, and the surface characterisation methods and surfaces employed are described.

Electron-metallographic studies of precipitation in an aluminium-zinc-magnesium alloy

The mechanism of sub-microscopic precipitation in an Al-Zn-Mg alloy selected for its maximum response to ageing has been studied by a standardized oxide-replica technique in a 100 kV. Philips Electron Microscope. Contrary to earlier conclusions, examination of the oxide replicas has been shown to reveal details of the precipitation process almost as clearly as the thin-foil transmission technique. The reported formation of spherical Guinier-Preston zones followed by the development of a Widmanstaetten pattern of precipitated platelets has been confirmed. The zones have, however, been shown to grow into the platelets and not to dissolve in the matrix as reported earlier. The precipitation process has been correlated with the Hardness/Ageing Time curve and the structure of the precipitates has also been discussed.

Studies on design, fabrication and reliability assessment of embedded passives on a high-density interconnect (HDI) organic substrate using a sequential build-up process

One of the foremost design considerations in microelectronics miniaturization is the use of embedded passives which provide practical solution. In a typical circuit, over 80 percent of the electronic components are passives such as resistors, inductors, and capacitors that could take up to almost 50 percent of the entire printed circuit board area. By integrating passive components within the substrate instead of being on the surface, embedded passives reduce the system real estate, eliminate the need for discrete and assembly, enhance electrical performance and reliability, and potentially reduce the overall cost. Moreover, it is lead free. Even with these advantages, embedded passive technology is at a relatively immature stage and more characterization and optimization are needed for practical applications leading to its commercialization.This paper presents an entire process from design and fabrication to electrical characterization and reliability test of embedded passives on multilayered microvia organic substrate. Two test vehicles focusing on resistors and capacitors have been designed and fabricated. Embedded capacitors in this study are made with polymer/ceramic nanocomposite (BaTiO3) material to take advantage of low processing temperature of polymers and relatively high dielectric constant of ceramics and the values of these capacitors range from 50 pF to 1.5 nF with capacitance per area of approximately 1.5 nF/cm(2). Limited high frequency measurement of these capacitors was performed. Furthermore, reliability assessments of thermal shock and temperature humidity tests based on JEDEC standards were carried out. Resistors used in this work have been of three types: 1) carbon ink based polymer thick film (PTF), 2) resistor foils with known sheet resistivities which are laminated to printed wiring board (PWB) during a sequential build-up (SBU) process and 3) thin-film resistor plating by electroless method. Realization of embedded resistors on conventional board-level high-loss epoxy (similar to 0.015 at 1 GHz) and proposed low-loss BCB dielectric (similar to 0.0008 at > 40 GHz) has been explored in this study. Ni-P and Ni-W-P alloys were plated using conventional electroless plating, and NiCr and NiCrAlSi foils were used for the foil transfer process. For the first time, Benzocyclobutene (BCB) has been proposed as a board level dielectric for advanced System-on-Package (SOP) module primarily due to its attractive low-loss (for RF application) and thin film (for high density wiring) properties.Although embedded passives are more reliable by eliminating solder joint interconnects, they also introduce other concerns such as cracks, delamination and component instability. More layers may be needed to accommodate the embedded passives, and various materials within the substrate may cause significant thermo -mechanical stress due to coefficient of thermal expansion (CTE) mismatch. In this work, numerical models of embedded capacitors have been developed to qualitatively examine the effects of process conditions and electrical performance due to thermo-mechanical deformations.Also, a prototype working product with the board level design including features of embedded resistors and capacitors are underway. Preliminary results of these are presented.

The Biopolitics of Gender

This dissertation inquires into the relationship between gender and biopolitics. Biopolitics, according to Michel Foucault, is the mode of politics that is situated and exercised at the level of life. The dissertation claims that gender is a technology of biopower specific to the optimisation of the sexual reproduction of human life, deployed through the scientific and governmental problematisation of declining fertility rates in the mid-twentieth century. Just as Michel Foucault claimed that sexuality became a scientific and political discourse in the nineteenth century, gender has also since emerged in these fields. In this dissertation, gender is treated as neither a representation of sex nor a cultural construct or category of identity. Rather, a genealogy of gender as an apparatus of biopower in conducted. It demonstrates how scientific and theoretical developments in the twentieth century marshalled gender into the sex/sexuality apparatus as a new technology of liberal biopower. Gender, I argue, has become necessary for the Western liberal order to recapture and re-optimise the life-producing functions of sex that reproduce the very object of biopolitics: life. The concept of the life function is introduced to analyse the life-producing violence of the sex/sexuality/gender apparatus. To do this, the thesis rereads the work of Michel Foucault through Gilles Deleuze for a deeper grasp of the material strategies of biopower and how it produces categories of difference and divides population according to them. The work of Judith Butler, in turn, is used as a foil against which to rearticulate the question of how to examine gender genealogically and biopolitically. The dissertation then executes a genealogy of gender, tracing the changing rationalities of sex/sexuality/gender from early feminist thought, through mid-twentieth century sexological, feminist, and demographic research, to current EU policy. According to this genealogy, in the mid-twentieth century demographers perceived that sexuality/sex, which Foucault observed as the life-producing biopolitical apparatus, was no longer sufficiently disciplining human bodies to reproduce. The life function was escaping the grasp of biopower. The analysis demonstrates how gender theory was taken up as a means of reterritorialising the life function: nature would be disciplined to reproduce by controlling culture. The crucial theoretical and genealogical argument of the thesis, that gender is a discourse with biopolitical foundations and a technology of biopower, radically challenges the premises of gender theory and feminist politics, as well as the emancipatory potential often granted to the gender concept. The project asks what gender means, what biopolitical function it performs, and what is at stake for feminist politics when it engages with it. In so doing, it identifies biopolitics and the problem of life as possibly the most urgent arena for feminist politics today.

Onttojen puiden lahopuukovakuoriaiset — kolmen pyydystyypin vertailu

Vanhat ja ontot puut ovat tärkeä elinympäristö monelle lahopuusta riippuvaiselle eliölajille. Onttoihin puihin on erikoistunut suuri määrä myös vaarantuneita ja harvinaisia hyönteislajeja, jotka elävät puun onkalon seinämillä tai onkalon pohjalle kerääntyvässä orgaanisessa aineksessa, ns. mulmissa. Tutkimuksen tavoitteena oli selvittää, mikä kolmesta pyydystyypistä (ikkuna-, vuoka- ja kuoppapyydys) soveltuu parhaiten onttojen puiden lahopuukovakuoriaisten pyyntiin. Lisäksi tavoitteena oli kartoittaa hyönteisnäytteiden ensimmäiseen laboratoriokäsittelyyn vaadittua aikaa. Tutkimuksessa oli mukana vanhoja rungostaan onttoutuneita lehmuksia, tammia ja vaahteroita pääkaupunkiseudun puisto- ja kartanoalueilta. Puiden onkaloiden sisään aseteltiin ikkuna-, vuoka- ja kuoppapyydyksiä, kaksi kutakin tyyppiä ja ne tyhjennettiin kolmen viikon välein touko-heinäkuussa 2006. Pyydyksiä oli siis yhteensä 90 per pyyntijakso. Kun näytteistä eroteltiin halutut hyönteislahkot (mukaanlukien kovakuoriaiset) niiden käsittelyyn käytetty aika kirjattiin ylös. Aineistosta tunnistettiin yhteensä 3825 kovakuoriaisyksilöä ja 212 lajia, joista lahopuusta riippuvaisia oli yhteensä 3398 yksilöä ja 121 lajia. Ikkunapyydyksissä esiintyi yhteensä 1639 yksilöä ja 140 lajia, vuokapyydyksissä 1506 yksilöä ja 134 lajia, kuoppapyydyksissä 680 yksilöä ja 111 lajia. Näytteiden käsittelyaikojen keskiarvot olivat 48,3 minuuttia ikkunapyydykselle, 65,5 minuuttia vuokapyydykselle ja 34,1 kuoppapyydykselle. Lajistokoostumuksen huomioiva ?-diversiteetti erosi huomattavasti pyydysten välillä, se oli 36,5 % ikkuna- ja vuokapyydysten välillä, 13,1 % ikkuna- ja kuoppapyydysten välillä ja 14,2 % vuoka- ja kuoppapyydysten välillä. Ikkuna- ja vuokapyydysten välillä ei havaittu tilastollisesti merkitsevää eroa saproksyylilajien (p<0,05), -yksilöiden (p<0,05) tai käsittelyaikojen (p<0,05) keskiarvoissa. Ikkuna- ja vuokapyydyksillä saatiin keskimäärin selvästi enemmän saproksyylilajeja ja –yksilöitä kuoppapyydykseen verrattuna. Kuoppapyydyksellä saatiin kokonaisyksilömäärään verrattuna suhteellisesti vähemmän saproksyylejä (59 %) kuin ikkuna- (69 %) ja vuokapyydyksillä (71 %). Ikkunapyydykset olivat tehokkain pyydystyyppi vertailtaessa pyydysten keräämää saproksyyliyksilömäärää suhteessa aineiston käsittelyn vaatimaan aikaan. Tehokkuus (yksilöä minuutissa) ikkunapyydykselle oli 0,74, vuokapyydykselle 0,43 ja kuoppapyydykselle 0,21. Ikkunapyydyksiä ei ole aikaisemmin käytetty puun onkalon sisällä hyönteisiä pyydettäessä vaan ne ovat aikaisemmissa tutkimuksissa roikkuneet onkalon ulkopuolella. Ikkunapyydykset kuitenkin toimivat erinomaisesti myös onkaloiden sisällä. Ikkuna- sekä vuokapyydys toimivatkin selkeästi paremmin lahopuukovakuoriaisten pyynnissä verrattuna kuoppapyydykseen, jonka poisjättäminen olisi kuitenkin tuottanut huomattavasti lajiköyhemmän aineiston. Mahdollisimman monimuotoisen onttojen puiden lahopuukovakuoriaislajiston keräämiseksi tulisi käyttää ikkuna- tai vuokapyydyksiä yhdessä kuoppapyydysten kanssa.