Bentonite clay is proposed to be a buffer material in the KBS-3 method of deep geological disposal of spent nuclear fuel in Sweden and Finland. It is essential to know the long term behaviour of the material when evaluating the safety performance of the barrier system. Therefore, various experiments and modelling have been carried out with bentonite in different conditions during the last decades. However, most of the laboratory experiments in controlled conditions last less than few years only.

In this study 15 years old compacted MX-80 bentonite samples were studied. They stayed closed in a copper canister in contact with low salinity groundwater both in aerobic and anaerobic conditions. After dismantling the experiment a thorough characterization was carried out, including analysis of chemical composition of bentonite and external solution, clay microstructure, mineralogy and microbial activity.

In this presentation the focus is on the microstructural features of the samples. Small-angle X-ray scattering (SAXS), nuclear magnetic resonance (NMR) and anion exclusion measurement were used to investigate the nano and micro porosity features of the material. The results are compared with similar analysis of MX-80 samples prepared in the laboratory and with short time equilibration with external solution. Calculations based on SAXS data give similar results but there are differences for NMR based results. This could be caused by dissimilarities of between the samples at the mesoscale level. No differences were observed between the oxic and anoxic conditions suggesting no influence of redox conditions on the bentonite microstructure.

We show that alloying with rare earth metals (REMs) can dramatically improve the machineability of a range of titanium alloys, even though the REM is not incorporated in the alloy matrix. The mechanism for this is that under cutting, shear bands are formed within which the nano-precipitates of REM are shear mixed. This lowers the melting point such that the mechanism of deformation changes from dislocation mechanism to localised amorphisation and shear softening. The material then fractures along the thin, amorphous shear-band. Outside the shear band, the REM remains as precipitates. The new alloys have similar mechanical properties and biocompatibility to conventional materials.

In this work polypyrrole (PPy) and its respective composite with functionalized multiwalled carbon nanotubes (PPy-MWCNT) was obtained by the chemical polymerization of the monomer pyrrole (PPy) in aqueous solution by the dropwise addition of a solution of ammonium persulfate (PSA). The obtained PPy as well as its composite (PPy-MWCNT) were used to prepare two self-assembled films (SA) by the immersion of ITO blades (Inidium Tin Oxide) into PPy and PPy-MWCNT dispersions with alternated immersions into Polystyrene sulfonate (PSS) dispersion, thus resulting in a bilayer. The SA films were produced with ten bilayers (alternated layers of PPy or its composite). The obtained films were characterized by Fourrier Transformed Infrared Spectroscopy (FTIR), UV-Visible analysis, voltammetric analyses (square wave and cyclic voltammetry) and Scanning Electron Microscopy (SEM). The SA films were evaluated to determine the chlorothalonil pesticide which is commonly used as anti-fouling agent in marine environments. The SWV results showed a reduction peak at around -0.8 to 1.2 V (according to pH). It was also observed a synergic effect of the composite film (PPy-MWCNT/PSS) to determine the chlorothalonil by increase of the peak currents.

Helium is produced in spent nuclear fuel by α-decays of actinides. After 10,000 years, the concentration of He accumulated in UO2 spent fuel is about 0.23 at.%. For direct disposal of spent nuclear fuel, consequences of helium build-up on the fuel matrix microstructure must be evaluated since it can modify the radionuclide release when water comes into contact with the spent fuel surface, after breaching of the disposal canister. An operational model has been proposed in order to evaluate the effect of helium on the microstructure of spent fuel in a repository. Based on conservative assumptions and different scenarios of bubble population, the calculated helium critical concentration, that could lead to a partial loss of integrity of the spent fuel pellet, is 0.37 at.%. However, observations on He-implanted UO2, α-doped UO2 pellets and natural analogues evidence a macroscopic damage only for He concentrations, which are more than one order of magnitude higher.

The electrophoretic transport of ions through single walled carbon nanotubes (SWCNTs) of diameters between 1.2 and 1.8 nm was studied for different monovalent chloride salts using microfluidic devices incorporating either a single or few SWCNTs in parallel. The ionic conductance was found to be about one order of magnitude higher than would be expected from simple bulk electrophoresis without any surface effect. Importantly, the ionic conductance measured for different cations did not scale with their bulk electrophoretic mobility thus indicating a selective cation transport through these sub-2 nm SWCNTs. The transport of Na+ was notably found to be favored in comparison to that of Li+, K+ and Cs+. These results highlight the influence of steric and surface effects induced by the nano-confinement on the transport of ions through sub-2 nm SWCNTs.

Flexible electronics has emerged as a very promising field, in particular,wearable, bendable, and stretchable strain sensors with high sensitivity which could be used for human motion detection, sports performance monitoring, etc. In this paper, a highly stretchable and sensitive strain sensor composed of reduced graphene oxide foam and elastomer composite is fabricated by assembly and followed by a polymer immersing process. The strain sensor has demonstrated high stretchability and sensitivity. Furthermore, the device was employed for gauging muscle-induced strain which results in high sensitivity and reproducibility. The developed strain sensors showed great application potential in fields of biomechanical systems.

Novel flexible composites were received by modification of polyurethane-carbon fiber interface. The modification was done by carbon nanotube grafting onto a surface of the fiber. The almost inevitable grafting-induced deterioration of the fiber properties was avoided due to sophisticated grafting technique, which includes introduction of a protective aluminium oxide layer. Re-enforced composites were fabricated with polyurethane as a matrix. The measurement of interfacial shear strength (IFSS) was used for estimation of polymer-fiber interface properties. It was shown that IFSS increased more than twice due to nanotube grafting. Thermal conductivity and mechanical properties enhancement was registered for composites with modified interface. Significant improvement of delamination resistance was proven for composites with modified polymer-fiber interface.

A facile hydrothermal method was used to synthesize molybdenum disulfide (MoS2) microspheres. The effect of hydrothermal reaction time on morphology and electrochemical properties of MoS2 microspheres was evaluated. X-ray diffraction showed presence of crystalline MoS2 structure, where content of crystalline phase was observed to increase with hydrothermal reaction time. Electrochemical properties of MoS2 were evaluated using cyclic voltammetry (CV) and galvanostatic charge-discharge in 3M KOH solution. Specific capacitance of nanostructured MoS2 was observed to be between 68 F/g and 346 F/g at different scan rates along with excellent cyclic stability. High power density (∼1200 W/kg) and energy density (∼5 Wh/kg) was observed for MoS2 sample synthesized for 24 hours of hydrothermal reaction time. Overall optimal electrocapactive performance was observed for sample prepared for 24 hours of reaction time. It is demonstrated that the obtained MoS2 microspheres with three-dimensional architecture has excellent electrochemical performances as electrode materials for supercapacitor applications.

Faster and more effective surface modification processes of polymer materials by UV/ozone treatment were investigated. The employment of ex-situ generated ozone and/or temperature control contributed to the faster and more effective modification. The UV/ozone treatment showed long-term stable hydrophilic surfaces for 6 months, in contrast to oxygen plasma treatment, which showed hydrophobic recovery. XPS analysis revealed that UV/ozone treatment with ex-situ generated ozone and temperature control added ester (-COOR) on COP sample compared to UV/ozone treatment without the additional ozone and temperature control.

Multiphysics simulations (COMSOL) of core-shell nanoarchitectures show that they can operate at 3 times the C-rate of micron scale thin film materials while still accessing 90% of an additive free cathode oxide material. A high performance Ge anode DC sputtered onto a Cu nanotube current collector is characterised. Volume expansion of Ge is alleviated and mechanical stability is enhanced due to the Cu nanotubes current collector.

A study of Mg2Sn thin film material expected a high Thermo-Electrical (TE) characteristics in Room Temperature (RT) range is presented. The single phase (cubic crystal) Mg2Sn thin film is successfully formed on a glass substrate at 550 degree C with the conventional magnetron sputtering process when a metal layer of silver (Ag) or indium (In) of less than a hundred nanometer thickness is pre-coated before the deposition of Mg2Sn. The pre-coated material of Ag or In is diffused into the Mg2Sn film. P-type doping for the Mg2Sn by Ag is successful in this process, but n-type doping for the Mg2Sn film by In is not. In addition, it is found on Ag doping films that the Seebeck coefficient doesn’t decrease with the increase of the conductivity due to Ag doping which is different from the dependency of Ag doping in the bulk of Mg2Sn.

A persistent challenge in multi-scale modeling of materials is the prediction of plastic materials behavior based on the evolution of the dislocation state. An important step towards a dislocation based continuum description was recently achieved with the so called continuum dislocation dynamics (CDD). CDD captures the kinematics of moving curved dislocations in flux-type evolution equations for dislocation density variables, coupled to the stress field via average dislocation velocity-laws based on the Peach-Koehler force. The lowest order closure of CDD employs three internal variables per slip system, namely the total dislocation density, the classical dislocation density tensor and a so called curvature density.

In the current work we present a three-dimensional implementation of the lowest order CDD theory as a materials sub-routine for Abaqus® in conjunction with the crystal plasticity framework DAMASK. We simulate bending of a micro-beam and qualitatively compare the plastic shear and the dislocation distribution on a given slip system to results from the literature. The CDD simulations reproduce a zone of reduced plastic shear close to the surfaces and dislocation pile-ups towards the center of the beam, which have been similarly observed in discrete dislocation simulations.

Nacre (mother of pearl) is an attractive model for the development of newmaterials. Its sheet structure of alternating layers of calcium carbonate and anorganic matrix confers it highly desirable properties such as high toughness andstrength. In this study, we produce a nacre-inspired composite material usingonly bacterially-produced components. Calcium carbonate is crystallized via theaction of ureolytic bacteria. After each crystallization event, we applybacterially produced γ-polyglutamate (PGA) to the sample, whichpromotes layering compared to the PGA-free control. We show that the combinationof these two compounds yields a layered material reminiscent of nacre, showing away towards the biotechnological production of new, nacre-inspiredmaterials.

Bi-epitaxial VO2 thin films with [011] out-of-plane orientation were integrated with Si(100) substrates through TiO2/TiN buffer layers. At the first step, TiN is grown epitaxially on Si(100), where a cube-on-cube epitaxy is achieved. Then, TiN was oxidized in-situ ending up having epitaxial r-TiO2. Finally, VO2 was deposited on top of TiO2. The alignment across the interfaces was stablished as VO2(011)║TiO2(110)║TiN(100)║Si(100) and VO2(110) /VO2(010)║TiO2(011)║TiN(112)║Si(112). The inter-planar spacing of VO2(010) and TiO2(011) equal to 2.26 and 2.50 Å, respectively. This results in a 9.78% tensile misfit strain in VO2(010) lattice which relaxes through 9/10 alteration domains with a frequency factor of 0.5, according to the domain matching epitaxy paradigm. Also, the inter-planar spacing of VO2(011) and TiO2(011) equals to 3.19 and 2.50 Å, respectively. This results in a 27.6% compressive misfit strain in VO2(011) lattice which relaxes through 3/4 alteration domains with a frequency factor of 0.57. We studied semiconductor to metal transition characteristics of VO2/TiO2/TiN/Si heterostructures and established a correlation between intrinsic defects and magnetic properties.

Tissue engineering scaffolding is the external media or structure in which cell growth, migration and reproduction is enabled in order to stimulate tissue regeneration. In order to promote tissue regeneration, scaffolding materials are required to have certain properties such as biocompatibility, adequate mechanical properties and surface topographical features in order to provide specific biological signals to promote cell attachment and proliferation [1].

Cellulose is the most abundant, inexpensive and readily available carbohydrate polymer in the world and it is traditionally extracted from plants or their wastes [2]. Although the plant itself is the major contributor of cellulose, various types of bacteria are able to produce cellulose and it is termed bacterial cellulose [3]. Bacterial cellulose is a well suited scaffold for tissue regeneration due to its biocompatibility, mechanical properties and its ability to be combined with other structures such calcium phosphates [4], which can create composites with intrinsic properties that meet the requirements of the different tissues of the human body [5].

Through additive manufacturing, highly complex structures can be created which are similar to those found in nature. This work will explore the different ways to produce biomimetic structures for tissue engineering applications through the combination of bacterial cellulose and additive manufacturing producing complex structures of a highly a biocompatible material for a range of different biomedical applications [6]. In addition to the manufacturing and processing techniques, the use of mango (juice/peel) as a complex carbon source for the production of bacterial cellulose was investigated.

The disposal of materials at the end of their lifecycle, especially for complex manufactured products, presents challenges in terms of both protecting the environment and human health. In particular, used automobiles are disposed of by removal of various component parts, followed by shredding. In this study, air particulates were collected over several days by DRUM impactor downwind of an automobile shredding plant, size separated, and analyzed by scanning and transmission electron microscopy (SEM and TEM), and energy-dispersive x-ray spectroscopy (EDXS), in order to determine their particle size distribution and corresponding chemical composition. Results for larger particles, ranging in size from 2.5 to 10.0 μm, showed mainly diatoms and salts, from the plant’s ocean side location, and aluminosilicates, consistent with geological sources. As particle size decreased from 10 μm to 0.09 μm, particle loading decreased, and composition shifted to mainly oxygen and sulfur, indicative of sulfates, which along with nickel and vanadium that were detected, could be attributed to emissions from nearby shipping traffic. Iron was found to be present, including in spherical particles that were ∼ 2 μm in diameter, indicating they originated from a high temperature process. Spherical iron particles also were found to correlate with plant operations, making them a useful “tracer” material for plant emissions. Lead, cerium, barium, chromium and zinc were also detected and their possible correlation to plant feedstocks is discussed. The implications of these results for the environment, particularly soil and water deposition, and for human health as a result of inhalation, are discussed.

The enhancement of photovoltaic efficiency by incorporation of down-shifting phosphor materials in optically active and inactive regions of solar modules is presented. Thin film photovoltaic modules suffer from various optical losses, including front glass reflectance, thermalization loss of absorbed high energy photons, window layer absorption, and the loss of photons to scribe regions. There have been various efforts to improve the performance of solar modules by application of down-shifting (DS), down-converting, and up-converting materials systems. Here we show results towards the development of a low-cost phosphor film system tuned to the solar spectrum and specifically designed for CdTe thin film modules.