This paper outlines updates to and evaluation of a learning module that incorporates a molecular dynamics (MD) simulation tool with a physical lab to introduce students to the atomic-level processes that are responsible for plastic deformation. Sophomore materials science and engineering (MSE) students at Purdue University get experience with both a physical laboratory, where they perform and analyze tensile tests of macroscopic samples, and a simulation laboratory, where they run and analyze MD simulations of tensile tests of metal nanowires. By integrating these two activities and discussing reasons for the large difference in yield stress, students may build an intuitive feel for how plastic deformation is linked across length scales

Self-assembling peptides (SAPs) have the ability to spontaneously assemble into ordered nanostructures enabling the manufacture of ‘designer’ nanomaterials. The reversible molecular association of SAPs has been shown to offer great promise in therapeutics via for example, the design of biomimetic assemblies for hard tissue regeneration. This could be further exploited for novel nano/micro diagnostic tools. However, self-assembled peptide gels are often associated with inherent weak and transient mechanical properties. Their incorporation into polymeric matrices has been considered as a potential strategy to enhance their mechanical stability. This study focuses on the incorporation of an 11-residue peptide, P11-8 (peptide sequence: CH3CO-Gln-Gln-Arg-Phe-Orn-Trp-Orn-Phe-Glu-Gln-Gln-NH2) within a fibrous scaffold of poly (ε-caprolactone) (PCL). In this study an electrospinning technique was used to fabricate a biomimetic porous scaffold out of a solution of P11-8 and PCL which resulted in a biphasic structure composed of submicron fibers (diameter of 100-700 nm) and nanofibers (diameter of 10-100 nm). The internal morphology of the fabric and its micro-structure can be easily controlled by changing the peptide concentration. The secondary conformation of P11-8 was investigated in the as-spun fibers by ATR-FTIR spectroscopy and it is shown that peptide self-assembly into β-sheet tapes has taken place during fiber formation and the deposition of the fibrous web.

Vitreous materials are the overwhelming world-wide choice for the immobilisation of HLW resulting from nuclear fuel reprocessing due to glass tolerance for the chemical elements found in the waste as well as its inherent stability and durability. Vitrification is a mature technology and has been used for high-level nuclear waste immobilization for more than 50 years. Borosilicate glass is the formulation of choice in most applications although other formulations are also used e.g. phosphate glasses are used to immobilize high level wastes in Russia. The excellent durability of vitrified radioactive waste ensures a high degree of environment protection. Waste vitrification gives high waste volume reduction along with simple and cheap disposal facilities. Although vitrification requires a high initial investment and then operational costs, the overall cost of vitrified radioactive waste is usually lower than alternative options when account is taken of transportation and disposal expenses. Glass has proven to be also a suitable matrix for intermediate and low-level radioactive wastes and is currently used to treat legacy waste in USA, and NPP operational waste in Russia and South Korea. This report is also outlining IAEA activities aiming to support utilisation of vitreous materials for nuclear waste immobilisation.

Silicon heterojunction (Si-HJT) solar cells are one of the most efficient silicon-based solar cells, due largely to their high open-circuit voltages. For the transparent conductive oxide (TCO) layers, there is a design trade-off between their conductance and their parasitic light absorption, and this trade-off can be a performance-limiting factor for Si-HJT solar cells. It has been demonstrated that silver nanowire (AgNW) networks with superior optical and electrical performances, can complement TCOs. To evaluate the performance of AgNW-TCO hybrid electrodes for Si-HJT cells, it is beneficial to numerically simulate and optimize the optical and electrical performances of the entire device. However, the dimensions of the AgNWs are massively different to the dimensions of the other components of the cells, making individual modeling methods incapable. In this paper, we use an angular matrix framework (AMF) to resolve the challenge, where matrices are used to describe the transition of the angular distribution of the light when it is reflected or transmitted at the interface, or absorbed in the bulk. These matrices pass optical information between nanoscale and microscale components of the cell structure. Using AMF, we calculated the optical properties of the devices, and demonstrated that the AgNW-TCO electrode has advantages over a TCO electrode. Guidance on how the optimization of the composite electrode can be achieved was provided.

X-ray diffraction pattern collected with two-dimensional detector contains the scattering intensity distribution as a function of two orthogonal angles. One is the Bragg angle 2θ and the other is the azimuthal angle about the incident x-ray beam, denoted by γ. A 2D diffraction pattern can be integrated to a conventional diffraction pattern and evaluated by most exiting software and algorithms for conventional applications, such as, phase identification, structure refinement and 2θ-profile analysis. However, the materials structure information associated to the intensity distribution along γ direction is lost through the integration. The diffraction vector approach has been approved to be the genuine theory in 2D data analysis. The unit diffraction vector used for 2D analysis is a function of both 2θ and γ. The unit diffraction vector for all the pixels in the 2D pattern can be expressed either in the laboratory coordinates or in the sample coordinates. The vector components can then be used to derive fundamental equations for many applications, including stress, texture, crystal orientation and crystal size evaluation.

Zinc oxide thin films were prepared via the sol-gel spin-coating method with the use of a spin processor. The film’s annealing parameters were varied to study their impact on the final film morphology and electrical properties. Characterization of the structural properties of the samples was carried on a X-ray diffractometer (XRD) and scanning electron microscopy. Electrical characterization was obtained with the use of a four point probe. Optical characterization of the samples was carried on a UV-Vis-NIR Spectrophotometer. Samples annealed under a cover are observed to have a higher transmission percentage on the visible light range while having a very small grain size and small relative resistivity. Samples annealed under standard atmospheric conditions show a larger grain size and resistivity, and correlated to it, a smaller transmission percentage. Samples annealed under vacuum prove to have a much more reduced optical, electrical, and structural properties when compared to the rest of the samples.

Porous ceramics have been widely used under extreme environments due to their high strength, good thermal shock resistance, and excellent corrosion resistance. Recently, silicon aluminum oxynitride (SiAlON) ceramic, a solid solution of Si3N4 with AlN, SiO2, and Al2O3, attracted our interest because of its superior mechanical and physical properties for applications under extreme environments (i.e., high temperature, high pressure, excellent mechanical wear, and low PH). However, in spite of its many unique properties, porous SiAlON production has not been scaled up sufficiently to meet industrially relevant quantities due to its high synthesis cost and the difficulty of manufacturing articles. Here, we report on a scalable two-step carbothermal reduction and nitridation (CRN) method to synthesize mechanically robust SiAlON ceramic materials with controlled porosity levels. The morphologies and chemical composition of the synthesized porous SiAlON ceramics were characterized using SEM, XRD, EDAX, and microprobe analysis. In addition, the flexural strength of the engineered porous SiAlON ceramics is also reported in this paper.

For biological and mechanical systems involving moving parts, surface slipperiness is often a critical attribute for their optimal functions. Surface grafting with hydrophilic polymers is a powerful means to render materials slippery in aqueous environment. In “inverted grafting-to approach”, the hydrophilic polymer chains of amphiphilic diblock copolymers dispersed within a poly(dimethylsiloxane) (PDMS) network are selectively segregated upon exposure to aqueous solution. This allows formation of extremely stable brush-like polymer layers. Tribological application of inverted grafting-to approach was successfully demonstrated with PDMS-block-poly(acrylic acid) (PDMS-b-PAA) dispersed within thin PDMS films on PDMS blocks by showing friction coefficients (µ) of ca 10-2 to 10-3, depending on the load, pH and buffer salinity in the absence of other external re-supply of PAA chains. Further manipulations of the thin PDMS film incorporating PDMS-b-PAA to optimize the tribological properties are presented. Lastly, first trials to employ PAA-grafted PDMS surface to generate in-vitro mucosae model are also presented and discussed.

Titration of bentonite, or clay materials in general, can be carried out in two ways, namely by semi-continuous method and batch method. This study compares these two methods, and, in addition, presents the results of two different evaluation and regression procedures used for fitting of experimental titration curves and for calculation of corresponding parameters. Bentonites B75 and S65, and montmorillonite SAz-1, were chosen for this study. Regarding the semi-continuous method, the technique developed by Wanner et al. was used. As for the batch method, two-week contact time for selected solid/liquid ratio 1 g per 250 ml was used on the base of preliminary experiments. The evaluation of result obtained using the batch method with back titration correction gave more relevant data, on the other hand, with the use of this method is connected a risk of solid phase dissolution. The chemical equilibrium model (i.e. non-electrostatic), incorporated into codes (I) PHREEQC + UCODE_2005, and (II) PDNLRG.fm (code package STAMB) + software FAMULUS, was used to the evaluation of the titration curves. The codes mentioned give only slightly different resulting values in the case of batch method.

Disodium terephthalate (Na2TP), which is a disodium salt of terephthalic acid, is very promising organic electrode material for Na-ion batteries. We present an ab initio study of Na binding mechanism with Na2TP molecule. Specially, we provide the interaction energy of Na atom(s), effect of Na concentration on interaction energy, electronic properties of clean and Na attached Na2TP, and Na binding mechanism with Na2TP. We show that up to eight Na atoms can be attached to a single Na2TP molecule. The interaction energy of Na atoms varies from -0.79 to -0.66 eV with attachment of one to eight Na atoms. The adsorbed Na atom interacts with O atoms of carboxylate group and Na atoms of the salt molecule. The interaction between adsorbed Na and C atoms of the molecule is found to be not important for Na bindings. Attachment of a single Na atom generates a singly occupied orbital which becomes doubly occupied with attachment of second Na atoms. Attachment of more than two Na atoms leads to electron occupation of bonding orbitals formed between Na atoms and the carboxylate groups.

This paper presents a comparative study on the effects of plasma type and duration on the contact angle of silicon (Si) and fused silica (FS) for the deposition of Poly (3,4 ethyldioxythiophene) Polystyrene Sulfonate (PEDOT:PSS) via drop casting. The two methods used to measure contact angles were goniometry and profilometry. Both methods agreed that the lowest contact angles were given by: 1) 30 seconds in nitrogen/oxygen mix for Si substrates, and 2) 10 minutes in pure oxygen plasma for FS substrates.

Sodium bismuth titanate (Na0.5Bi0.5TiO3: NBT) a lead free piezoelectric; exhibits promising features such that it could be an alternate to lead based piezoelectrics. In this work, we report the microstructural influence on piezoelectric and leakage current behavior of NBT thin films grown by pulsed laser ablation (PLD). Various microstructural features like coarse faceted grains and fine spherical grains was achieved by effective optimization of substrate temperature and oxygen partial pressures. The studies reveals that, leakage current of NBT thin films were dominated by interface limited modified Schottky emission type of conduction. The piezoelectric domain studies reveal that for NBT thin films with fine spherical grain the domain pattern was highly dominated by the morphology and in the case of coarse faceted grains the domains were relatively large and the domains were extending beyond the grain boundaries.

Iron and nickel oxidation state and coordination in complex sodium aluminophosphate based glasses suggested as potential matrices for immobilization of legacy high level waste currently stored in stainless steel tanks at PA «Mayak» (Ural reg., Russia) were determined by X-ray absorption fine structure spectroscopy (XAFS: XANES/EXAFS). The glasses containing (wt.%) 20-30 Na2O, 6-12 Al2O3, 40-52 P2O5, 2-5 Fe2O3, 1-3 NiO, 0-6 B2O3, 10-15 other waste oxides produced by quenching of their melts were fully amorphous or contained minor Fe and Ni free phases. Fe in the glasses was found to be predominantly trivalent with an average Fe-O distance and a coordination number (CN) in the first shell of 1.94 to 1.97 Å and 5.2 to 5.8, respectively, mostly in octahedral oxygen environment. Ni is divalent in all the glasses and has in the first shell an average Ni-O distance and CN of 1.97 to 2.03 Å and 4.9 to 5.6, respectively. The first shell of both Fe and Ni is somewhat distorted. The second and further coordination shells are weakly appeared exhibiting no clustering and homogeneous distribution of Fe and Ni ions in the glass network. The data on Fe obtained are in good agreement with those from Mössbauer study of same glasses. After annealing glasses were partly devitrified and interpretation of XAFS data is strongly complicated due to Fe and Ni partitioning among crystalline and vitreous phases.

Flexible zinc-air batteries were fabricated using an inexpensive screen-printing technique. The anode and cathode current collectors were printed using commercial nano-silver conductive ink on a polyethylene terephthalate (PET) substrate and a polypropylene (PP) membrane, respectively. Air cathodes made of blended carbon black with inexpensive metal oxides including manganese oxide (MnO2) and cerium oxide (CeO2), were studied. The presence of the metal oxides in the air cathodes enhanced the oxygen reduction reaction which is the most important cathodic reaction in zinc-air batteries. The battery with 20 %wt CeO2 showed the highest performance and provided an open-circuit voltage of 1.6 V and 5 – 240 mA.cm-2 ohmic loss zone. The discharge potential of this battery at the current density of 5 mA.cm-2 was nearly 0.25 V higher than that of the battery without metal oxides. Finally, the battery was tested for its flexibility by bending it so that its length decreased from 2.5 to 1 cm. The results showed that the bending did not affect characteristics on potential voltage and discharging time of the batteries fabricated.

Diatoms are the most abundant resource of biosilica on Earth. These microalgae are encased in a 3-D amorphous silica “shell” called frustule whose size and morphology is strictly dependent on the diatom species. Naturally nanostructured biosilica from diatoms exhibit unique adsorption and confinement properties useful for delivery of molecules of pharmacological interest.In this work fossil biosilica was used as a carrier for Ophiobolin A (a fungal macrolide with anticancer and antiparasitic properties), with the aim to develop a model system of Ophiobolin A loading / delivery. Ophiobolin A delivery properties of fossil diatoms were investigated by spectophotometric analyses.

Dismantling of old reactors and the management of radioactive graphite wastes are becoming increasingly important issues for a number of IAEA Member States. Exchange of information and research cooperation in resolving identical problems between different institutions contributes towards improving waste-management practices, their efficiency, and general safety. The IAEA Coordinated Research Project (CRP) under the title ’Treatment of Irradiated Graphite to Meet Acceptance Criteria for Waste Disposal’ was conducted during 2010-2014 and has involved 24 organisations from ten Member States [1]. The CRP has explored both innovative and conventional methods for graphite characterisation, retrieval, treatment, and conditioning technologies and produced an IAEA technical document [2] which has identified a number of unresolved scientific and technical issues such as the need to:

• 1. Improve the scientific understanding required on creation, chemical form, location and release behaviour (transport models) of radionuclides;

• 2. Improve predictive models of radioisotope behaviour;

• 3. Ensure that sampling programmes are statistically representative of the totality of the graphite to be disposed of;

• 4. Establish an accurate radionuclide inventory;

• 5. Consider novel alternative dismantling and treatment strategies.

The CRP promoted the exchange of technical information on R & D activities and will facilitate practical application for treatment and conditioning of graphite waste. The collaboration continues under the IAEA International Decommissioning and Predisposal Networks (IDN and IPN).

CMOS-compatible fabrication and etching processes are often used in subwavelength grating structures manufacturing, it normally generates tapered sidewall profile of the gratings. In this work, we have studied the impacts on resonance mode characteristics of subwavelength grating structures due to the tapered sidewall profile, as well as grating with high aspect ratio. Our simulation results have revealed that both of these two factors play important roles on the resonance mode behavior of subwavelength grating devices. We also discussed the mechanism between the guided mode resonance and the grating cavity mode resonance. Our study will provide guidance for a series of integrated photonics devices applications, such as compact optical filter, photonics amplifier, and lasers, while the realistic subwavelength grating structure is considered.

Educators are advocating a variety of 21st century technologies to increase student engagement and prepare them for the modern workplace. As part of this effort this paper describes the development of several introductory laboratory activities which enhance online collaborative skills in the context of group collaborations. The experiments mostly deal with measurement and error in the context of mathematical modeling. They inculcate online collaborative skills including group writing, collection of experimental data, student feedback, and assessment using forms, spreadsheets with data pooling, real-time graphing/computations, and discussions using chat. These are all available in Google Drive, a free cloudbased application. We have also introduced student collaborative-pair computational spreadsheet assignments, and results of two projects in general chemistry are presented. Building formative assessment into these activities allows for immediate adjustment to instruction. This approach could be used from middle school through the undergraduate level. It can be implemented both in informal education or formal classroom settings by enhancing interactions with remote partners. Student evaluations have been very positive for the variety of activities, as well as from workshop feedback from high school teachers.

The set of oscillatory resonance AFM modes is expanded with frequency modulation mode and frequency imaging in amplitude modulation mode. The backgrounds of these modes are discussed and their capabilities are compared on the practical examples. The data show how these techniques complement the amplitude modulation with phase imaging. The frequency imaging enhances the compositional mapping of heterogeneous samples. Frequency modulation mode provides a superior capability in imaging at low tip-sample forces.

Thermoelectric properties of segmented nanowires and nanobelts are studied by means of the Kubo-Greenwood formula and a real-space renormalization plus convolution method. The tight-binding and Born models are respectively used for the calculation of electronic and lattice thermal conductivities. In particular, we investigate the thermoelectric figure of merit (ZT) of periodic and quasiperiodically segmented nanowires with two different cross sections, where the segments of the quasiperiodic one are ordered following the Fibonacci sequence. The results show an increase of ZT when the cross section area of nanowires diminishes. In addition, we present results of ZT in segmented nanobelts with an inhomogeneous cross section. For both nanowires and nanobelts, the quasiperiodicity seems to be an important enhancing factor of ZT.