We present some recent results of a systematic study regarding polyaniline-based nanocomposites with detonation nanodiamond as guest component. The peculiar properties of such crystalline nanomaterial not only help in improving the mechanical and thermal properties of the host polymeric matrix, but also influence polymerization mechanism, modifying the morphological features of the polymers. Induced by the nanodiamond presence, the final nanocomposites show a prominent arrangement of polymer segments into tubular forms and a subsequent structural organization suitable for many technological applications.

Lasing characteristics of a single Zinc oxide (ZnO) nanosheet and a single ZnO nanowire were investigated by an ultraviolet light excitation. ZnO nanocrystals were synthesized by chemical vapor deposition (CVD) method, and those ZnO nanocrystals were excited by a third-harmonic Q-switched Nd:YAG laser beam (355 nm, 5 ns). The emission spectra from a single ZnO nanocrystal was collected by an objective lens with a magnification factor of 100 or 50, coupled with a spectrometer with a light fiber. The area observed by the spectrometer is about 10 μm in diameter, and therefore the emission spectra from a single ZnO nanocrystal can be observed. The emission spectra showed the obvious lasing characteristics having mode structure and a threshold for lasing. The lasing threshold power density of a ZnO nanosheet and a ZnO nanowire were measured to be about 60 kW/cm2 and 150 kW/cm2, respectively. ZnO nanosheet can be a superior laser medium due to the lower threshold for lasing compared to the threshold of the ZnO nanowire. However, since the lasing spectra had mode structure, a single-longitudinal mode lasing would be required for a practical application. The single longitudinal mode lasing can be realized by a nanomachining of a grating on the ZnO nanocrystal surface due to distributed bragg reflector (DBR) laser. The minimum DBR pitch was estimated to be about 81 nm, which can be machined by focused-ion beam (FIB) focused up to 7 nm at minimum, and therefore, we demonstrated the nanomachining on a single ZnO nanowire. However, the single-longitudinal mode lasing was not observed so far, and thus optimization of experimental conditions such as the DBR pitch, ion dose amount and increasing the number of repetition of DBR would be required.

Reduction in the operating temperature of solid oxide fuel cells (SOFCs) allows for the use of ferritic stainless steels as the interconnect material. However, cathode poisoning due to volatilization of chromium from the oxide scale formed on these alloys requires the use of a ceramic coating on the alloy. The reaction layer formed between the coating and the alloy affects the performance of the fuel cell, so the composition and properties of this layer must be considered in selecting the alloy and coating compositions. In this paper, the factors relevant to selection of the alloy/coating materials and the effect of the alloy-coating interaction on these factors are discussed.

A bentonite buffer is a part of the engineering barrier system of the geological disposal concept for spent nuclear fuel in Finland. The chemical conditions in the bentonite porewater determine the solubility, speciation and diffusion/sorption behaviour of the radionuclides in the bentonite. The OH-groups on the edge sites of the montmorillonite, the main component of bentonite, can buffer the pH conditions especially in the case that the buffering capacity of the accessory minerals is small. In this work, the pH conditions created by the interaction of sodium montmorillonite and an acetate buffer solution were studied experimentally in batch experiments and in compacted sodium montmorillonite. In the experiment with the compacted sample, the ends of an 18.4 mm long cylinder were exposed to an external solution of 0.3 M NaCl and 0.1 M acetate adjusted to pH 5 with NaOH. The effects were monitored by measuring the pH in the montmorillonite sample at 5 mm and 9.2 mm from the solution-montmorillonite interface as a function of time. The batch experiment was modelled considering the surface reactions of montmorillonite and the dissolution reactions of calcite and the added constituents to explain the observed phenomena.

With the appropriate surface treatments, graphene sheets can be separated from graphite material and the layer-to-layer distance can be extended. In the present work, graphene nanosheets (GNS) were separated from graphite by an improved, safer and mild method including the steps of oxidation, thermal expansion, ultrasonic treatment and chemical reduction. For the production of advanced polymer nanocomposites, the distinguished properties of GNS were combined with the structural properties of conducting polypyrrole by the proposed simple and low-cost fabrication technique. The changes in surface morphologies and surface functional groups were estimated by controlling the polymer coating on graphite oxide (GO) sheets, expanded GO and GNS.

Today polysaccharide based hydrogel nanocomposites are receiving high importance as biomaterials for drug delivery. Inorganic nanoparticles (NPs) are incorporated into the polymer matrix to provide novel functionalities to the hydrogels. However, the effect of nanofillers on the release properties has not been totally understood. In this work, we investigate the influence of inorganic functional nanofillers (Fe3O4 and Au NPs) with variable size and shape on the structure of κ-carrageenan hydrogels and on the kinetics and release mechanism of methylene blue (MB) as model drug. It was shown that, depending on the nature of the nanofiller incorporated, and for equivalent nanofiller content, the mechanism of MB release can be adjusted either to by diffusion or polymer relaxation mechanism. The mechanism of the MB release was found to be determined by the strength and microstructure of the gel network and extent of gel swelling, which are affected by the extent of incorporation of the nanofillers.

High performance polymer network gels consisting of tetra-armpoly(ethyleneglycol) (Tetra-PEG) gels were fabricated via a moduleassembling method and their mechanical properties and structure wereinvestigated by stretching and compression measurements, dynamic mechanicalmeasurements, and small-angle neutron scattering (SANS). It was found thatTetra-PEG gels are nearly-ideal polymer network with negligible fractions ofdefects and entanglements. SANS intensity functions indicated that thenetwork structure was uniform free from spatial inhomogeneities. It isdeduced that this uniform structure is ascribed to its unique preparationmethod, i.e., module assembling method (cross-end-coupling oftetra-functional macromers with complementary functional groups).Characteristic properties originated from the near-ideality as polymernetworks are demonstrated, including its application to ion gels, i.e.,polymer network in ionic liquid.

Preparing porous biodegradable structures from shape memory polymers can combine the structure-defining properties of porous structures with the minimally invasive implanting possibilities of shape memory polymers. In this study, porous biodegradable shape memory structures were prepared using photo-crosslinked networks based on poly(D,L-lactide-co-trimethylene carbonate). The characteristic shape memory properties of the structures, such as their shape fixity at a low temperature of 0 o C and their full shape recovery upon heating to physiological temperatures, were excellent. This makes these biodegradable and biocompatible structures very well-suited for use as self-deploying implants in medical applications like tissue engineering, drug delivery and the support of soft tissues.

We report a study on catalytic water oxidation by cobalt in oxygen ligand environments because such systems are as promising as any in the water oxidation component of solar fuel production. We have re-examined the catalytic activity of Co(II) in aqueous solution using either [Ru(bpy)3]3+ as a stoichiometric oxidant or in visible-light-driven reactions with persulfate as a sacrificial electron acceptor. In both systems a distinctive induction period is observed. A simple kinetic model is proposed that describes the experimental data well. The presence of an induction period is explained by relatively slow formation of the true catalyst from aquacobalt(II).

The infiltration of dissolved dyes into vertically aligned carbon nanotube arrays (va-CNT) is reported. The ultra hydrophobic surface of the CNT forest can be wetted and hence infiltrated for an appropriate choice of solvent. The dye-infiltrated CNT array forms a well ordered bulk-heterojunction structure for organic solar cells in which the CNT can act as a large electrode or, for appropriate energy levels, as an acceptor material. Derivatives of the small molecule copper phthalocyanine or the polymer poly(3-hexylthiophene) were used as dyes. Drop coating was chosen as the infiltration technique resulting in a completely embedded CNT forest. Field emission secondary electron microscopy analysis illustrates the final layer quality. Common electrical characterization under AM1.5 illumination proves photosensitivity and implies photovoltaic behavior of the composite.

In recent years, nuclear waste management has become a fundamental issue in the nuclear energy production cycle. Tomographic Gamma Scanner (TGS) is an essential tool for nuclear waste characterization. It is crucial to rely on local support and cost effective solutions; for this reasons, we are designing our TGS system based on local technology. In this work, we present a study of different geometries and instrumentation chain parameters to design a TGS.

A set of Monte Carlo simulations were performed to evaluate energy and spatial resolution limitations of scintillator, CZT (Cadmium Zinc Telluride), and HPGe (high purity germanium) detectors. Collimator and detector geometries were studied to maximize the characteristics of the system. In this study, a phantom of 137Cs and 60Co was utilized to evaluate the overall performance of the proposed TGS system. In addition, the impact of electronic instrumentation chain and image reconstruction algorithms was taken into account.

In this study, the effect of dry oxidation on the electrochemical properties of carbon nanotube arrays is investigated. Oxygenated surface functional groups were introduced to the arrays by oxygen plasma treatment, where their surface concentrations were varied by controlling the exposure time. The finding presented herein shows an augmentation of nearly thirty times in term of specific capacitance when the arrays are oxidized. Similar behavior is also observed in the non-aqueous electrolytes where the specific capacitance of the oxidized carbon nanotube arrays is measured more than three times higher than that of the pristine ones. However, overexposure to oxygen plasma treatment reverses this effect. At such high oxidation level, the damage to the graphitic structure becomes more pronounced such that the capacitive behavior of the arrays is overshadowed by their resistive behavior. These findings are important for further development of carbon nanotube based electrochemical capacitors.

Zinc oxide (ZnO) is a semiconductor that emits bright UV light, with little wasted heat. This intrinsic feature makes it a promising material for energy-efficient white lighting, nano-lasers, and other optical applications. For devices to be competitive, however, it is necessary to develop reliable p-type doping. Although substitutional nitrogen has been considered as a potential p-type dopant for ZnO, recent theoretical and experimental work suggests that nitrogen is a deep acceptor and will not lead to p-type conductivity. In nitrogen-doped samples, a red photoluminescence (PL) band is correlated with the presence of deep nitrogen acceptors. PL excitation (PLE) measurements show an absorption threshold of 2.26 eV, in good agreement with theory. The results of these studies seem to rule out group-V elements as shallow acceptors in ZnO, contradicting numerous reports in the literature. Optical studies on ZnO nanocrystals show some intriguing leads. At liquid-helium temperatures, a series of sharp IR absorption peaks arise from an unknown acceptor impurity. The data are consistent with a hydrogenic acceptor 0.46 eV above the valence band edge. While this binding energy is still too deep for many practical applications, it represents a significant improvement over the 1.4-1.5 eV binding energy for nitrogen acceptors. Nanocrystals present another twist. Due to their high surface-to-volume ratio, surface states are especially important. In our model, the 0.46 eV level is shallow with respect to the surface valence band, raising the possibility of surface hole conduction.

Higher manganese silicide (HMS) is a low-cost and eco-friendly thermoelectric material available for recovering waste heat of 500 to 900 K. In this research, we tried to uniformly disperse the alumina nanoparticles (ANPs) in the HMS matrix to reduce the thermal conductivity and to improve the thermoelectric performance. Influence of addition of ANPs on the thermoelectric properties was investigated. It was confirmed that ANPs were uniformly dispersed in the HMS grain boundary. The lattice thermal conductivity was reduced by adding ANPs. As a result, the maximum thermoelectric performance of ZT=0.58 was achieved at about 800 K by adding 1 vol% of ANPs. The performance of ANPs-added HMS was improved about 25 %.

We have studied the growth rate enhancement of a-Si:H films using Si2H6 as a gas phase additive to SiH4+ H2 gas mixtures using relatively low pressure and standard 13.56 MHz RF power. With the addition of 1.7% Si2H6 in the gas mixtures (10% more Si atoms into the chamber), the a-Si:H film growth rate increased by ∼30% at 1.25 Torr and ∼60% at 2.5 Torr. The optical emission spectroscopy (OES) exhibits reduction of SiH* intensity with addition of Si2H6, which indicates the reduction of high energy electron impacts with Si containing molecules. The microstructural defect parameter (fraction of dihydride bonding in the film) appears to decrease with increase of RF power (i.e. increase of growth rate). Similar a-Si:H p-i-n cell efficiency 7-8% is achieved with and without enhanced i layer growth rate with the Si2H6additive.

In this paper we study the density of states in n-type N,N’-ditridecylperylene-3,4,9,10-tetracarboxylic diimide organic semiconductor using two different methods. The first one is based on the temperature dependence of the channel conductance in field-effect transistors. The second one is based on the subgap optical absorption coefficient measured using the Photothermal Deflection Spectroscopy technique. Both techniques allow estimating the distribution of localized states in the band gap of the semiconductor.

Network models of porous media are beneficial for predicting evolution of macroscopic permeability. This work proposes novel models based on truncated octahedral support. Systems with different pore coordination spectra for a given average coordination number can be constructed to match experimental data. This feature, and the allowed pore coordination of 14, make the proposed models more realistic and flexible than existing models with cubic support. Experimental data for two sandstones with substantially different properties are used to demonstrate the models’ ability to predict permeability. A strategy for calculating its evolution with internal damage is also described and results are presented. Developments of this strategy are suggested for deriving mechanism-based constitutive laws for engineering applications.

Single wall carbon nanotubes (SWCNTs) were incorporated into lithium ion battery anodes as conductive additives in mesocarbon microbead (MCMB) composites and as a free-standing support for silicon active materials. In the traditional MCMB composite, 0.5% w/w SWCNTs were used to replace 0.5% w/w SuperP conductive additives. The composite with 0.5% SWCNTs had nearly three times the conductivity which leads to improved electrochemical performance at higher discharge rates with a 20% increase in capacity at greater than a C/2 rate. The thermal stability and safety was measured using differential scanning calorimetry (DSC), and a 35% reduction in exothermic energy released was measured using the highly thermally conductive SWCNTs as an additive. Alternatively, free-standing SWCNT papers were coated with increasing amounts of silicon using a low pressure chemical vapor deposition technique and a silane precursor. Increasing the amount of silicon deposited led to a significant increase in specific capacity (>2000 mAh/g) and coulombic efficiency (>90%). At the highest silicon loading, the surface area of the electrode was reduced by over an order of magnitude which leads to lower solid electrolyte interface formation and improved safety as measured by DSC.