This study seeks to understand the low temperature reactions of the salt phase that occur during the vitrification of Hanford Low Activity Waste (LAW). Salts (such as nitrates, sulfates, carbonates, halides, etc.) play a key role in these low temperature reactions as they sequentially melt, decompose, and volatilize during batch-to-glass conversion. To further understand these complex processes, simplified LAW melts containing oxyanion salts (sodium salts of carbonate, sulfate, and/or nitrate) and early melting glass formers (boric acid) have been evaluated using thermal analysis, infrared absorption spectroscopy, and X-ray diffraction. Results from this study indicate that the volatilization behavior of particular salts is influenced by the presence or absence of other salts. NaNO3 volatilization is decreased by the presence of Na2SO4. The addition of either Na2SO4 or NaNO3 to the system may enhance the volatilization of Na2CO3. In all cases, Na2SO4 was retained after melting and was often found to be in two different crystalline phases upon quenching.

In this work we have analysed the conditions to grow epitaxial layers by Liquid Phase Epitaxy (LPE) from ternary Ga-As-P liquid phases on GaAs and GaP under initial conditions that are far away of the thermodynamic equilibrium. First, it is shown that the liquid-solid (L-S) interfaces are “stable” for all compositions of the liquid phases exclusively in contact with the GaP substrates. At the same time the elastic energy generated in mismatched GaAsyP1-y layers induces a reduction in the As content of the layer. Then, it should be expected that highly lattice mismatched epitaxial layers could be grown with small elastic energy, so that beyond certain stress the layers are initially non-planar having spatially separated but simultaneous local centres of nucleation and dissolution pits. These processes should cause a change on the composition of the liquid phase and, as consequence, the formation of the epitaxial islands with a composition gradient along its thickness. Our estimations show that in the case of contact of a Ga-As liquid phase with a GaP substrate the P content in the epitaxial islands increases with its thickness. The thermodynamic analysis was done with the CALPHAD method using SGTE data.

New data on microstructure of 16 years old (La, Pu)PO4 monazite ceramics doped with 8.1 wt% of 238Pu are presented. It is shown that the sample consists from at least two phases differing in La/Pu ratio and small precipitates of Pu-phosphate. Possible mechanisms of the compositional heterogeneity are discussed. Formation of Pu-containing rhabdophane after sample storage in air is observed. This phenomenon together with gradual mechanical destruction of the ceramic pellet formation of submicron particles will likely increase rate of radionuclides loss from the monazite-based waste form. X-ray emission lines produced by recoil uranium ions from Pu decay are analysed. It is suggested that careful examination of their relative intensities may provide important information about behaviour of "hot" recoils in nuclear waste forms.

In this study, plates of Inconel 600 superalloy were gas metal arc welded to investigate the effects of the welding process on the creep behavior of the welded samples and compare it to the creep behavior of samples in the as-received condition. Creep tests were performed at two temperatures (600 and 650 °C) with different stress levels. During the welding process, three distinctive microstructural zones are generated, i.e. welded material, heat affected zone, and base metal that may affect the properties of the welded joint. Microstructural, elemental analysis of samples was conducted using Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDS). The experimental results show that creep rupture preferentially occurs in the heat-affected zone of the base metal at 4 mm from the fusion line and that the creep behavior of welded samples is different from that of the base metal. These results can be used in the design of structural components to assure their structural integrity.

Successful disintegration of Chlorpyrifos pesticide by nearly monodisperse nano-gold photcatalyst (∼10 nm) for remediation of wastewater has been reported in current studies. Nano-Gold dispersion reaction with Chlorpyrifos solutions completes in 45 minutes at ambient temperature under the normal daylight and exhibit systematic variations in the solution color from wine red to pink to light sky blue and finally transforming into a transparent solution with fine precipitates. UV-Vis absorption studies correlates well with the systematic color changes as observed in the nano-gold treated Chlorpyrifos solutions with time. The characteristic localized surface plasmon resonance peak of nanogold dispersion observed at 529 nm red shifts to weak, medium and strong intensity peaks at ∼ 640 nm, 740 nm and 890 nm on increasing chlorpyrifos concentration owing to the aggregation of gold nanoparticles in small to bigger sized clusters. The fine turbidity in final transparent solution further confirms the aggregation of nanogold particles into stable bigger ensembles. IR transmission spectra of final transparent solutions showed disappearance of Chlorpyrifos νC-Cl and phosphorothioate functional group peaks indicating degradation of chlorpyrifos.

Most publications on (opto)electronic devices based on 2D materials rely on single monolayers embedded in classical 3D semiconductors, dielectrics and metals. However, heterostructures of different 2D materials can be employed to tailor the performance of the 2D components by reduced defect densities, carrier or exciton transfer processes and improved stability. This translates to additional and unique degrees of freedom for novel device design. The nearly infinite number of potential combinations of 2D layers allows for many fascinating applications. Unlike mechanical stacking, metal-organic vapour phase epitaxy (MOVPE) can potentially provide large-scale highly homogeneous 2D layer stacks with clean and sharp interfaces. Here, we demonstrate the direct successive MOVPE of MoS2/WS2 and WS2/MoS2 heterostructures on 2” sapphire (0001) substrates. Furthermore, the first deposition of large-scale MoS2/graphene and WS2/graphene heterostructures using only MOVPE is presented and the influence of growth time on nucleation of WS2 on graphene is analysed.

Diatoms are unicellular photosynthetic algae that autonomously fabricate a porous organized biosilica shell refined in billion years of evolution. They represent an inexhaustible source of low cost, biocompatible mesoporous silica. Despite the major advances in the genomic field, studies on diatom cell biology are still hampered by a lack of cellular tools. In particular, cell staining assays of diatoms viability are still limited or not well performant. Here we provide a phosphorescent organometallic iridium complex (Ir-Fcx) suitable to act as staining agent to detect diatoms viability.

Single crystal gold clusters (10 nm in size) have been collectively manipulated on mono- and bi-layered MoS2 islands (up to 20 µm) grown on SiO2 using AFM. On the monolayer the clusters tend to move in a direction corresponding to the zigzag alignment of the Mo and S atoms, and assemble into long striation patterns parallel to the scan direction. The distance between consecutive stripes is inversely proportional to the cluster concentration and size. A more detailed observation based on SEM shows that within each stripe the clusters remain separated by gaps of few nm in width possibly caused by electrostatic repulsion and/or the roughness of the SiO2 substrate (~2 nm). The stripes also proved to be thermally stable, preserving their superstructures up to 823 K. On the bilayer gold clusters are much less prone to move and assemble into stripes. These results suggest that the formation of nanostructures resulting from collective manipulation of metal clusters can be oriented by a properly chosen scan path in a rather straightforward way (as compared to one-by-one displacement of single clusters). The goal of forming µm-long but nm-thin wires with a geometrically defined shape could be easily reached with the use of smoother substrates or TMD materials with lesser charge transfer to metals adsorbed on them.

The self-assembly of optically active building blocks into functional nanocrystals as high-activity photocatalysts is a key in the field of photocatalysis. Cobalt porphyrin with abundant catalytic properties is extensively studied in photocatalytic water oxidation and CO2 reduction. Here, we present the fabrication of cobalt porphyrin nanocrystals through a surfactant-assisted interfacial self-assembly process using Co-tetra(4-pyridyl) porphyrin as building block. The self-assembly process relies on the combined noncovalent interactions such as π-π stacking and axial Co-N coordination between individual porphyrin molecules within surfactant micelles. Tuning different reaction conditions (temperature, the ratio of co-solvent DMF) and types of surfactant, various nanocrystals with well-defined 1D to 3D morphologies such as nanowires, nanorods and nano hexagonal prism were obtained. Due to the ordered accumulation of molecules, the nanocrystals exhibit the properties of the enhanced capability of visible light capture and can conduce to improve the transport and separation efficiency of the photogenerated carriers, which is important for photocatalysis. Further studies of photocatalytic CO2 reduction are being performed to address the relationship between the size and shape of the nanocrystals with the photocatalytic activity.

Ideal two-dimensional (2D) Heisenberg magnets lack long range magnetic order. However, the XY model with spins confined to a plane shows a topological phase transition at a finite temperature corresponding to binding and unbinding of vortices. Experimental evidence for such Berezinskii-Kosterlitz-Thouless (BKT) transitions has been difficult to obtain in condensed matter systems, where, even a weak interlayer coupling that is invariably present leads to long-range order, pre-empting the BKT transition. The BKT signatures are still discernible above the long-range ordering temperature, however, in the characteristic exponential temperature dependence of the coherence length of the fluctuations. In this work we report that an applied magnetic field can induce such BKT correlations not only in quasi 2-dimensional systems but also in nominally 3-dimensional manganites undergoing antiferromagnetic transitions. We arrive at this unexpected conclusion based on our studies of temperature dependence of electron paramagnetic resonance (EPR) linewidth ΔH(T) of Cr3+ doped bismuth strontium manganite Bi0.5Sr0.5Mn1-xCrxO3 (x= 0.04, 0.1) (BSMCO04 and BSMCO10).

In this study, zinc oxide nanoparticles (ZnO NPs) in powder and in thin film were successfully synthesized first time using an eco-friendly, simple and cost effective green synthesis method mediated by corn husk (Zea mays) extract as an effective chelating agent, and zinc nitrate hexahydrate as precursor. Diverse characterizations techniques such as High Resolution – Scanning Electron Microscopy (HR-SEM), Energy Dispersive X- rays Spectroscopy (EDS), X-Rays Diffraction (XRD), and UV – Vis – NIR spectroscopy as well as Photoluminescence (PL) were investigated to confirm ZnO NPs nature. For the ZnO NPs powder, highly crystalline ZnO nanoparticles (ZnO NPs) annealed at 500°C which are 48.635 nm in particles size were characterised by HR-SEM and XRD analysis. The structure morphology and the constituents of the resultant ZnO powder were investigated respectively by HR-SEM and EDS. UV – Visible spectroscopy analysis was investigated on the optical band gap of ZnO NPs, which was calculated to be 3.31 eV. This result indicates that ZnO NPs can be used in metal oxide semiconductor-based devices. For the ZnO NPs thin film, XRD patterns of hexagonal wurtzite structure with c/a ratio about of 1.60 and μ – parameter of 0.38 were obtained. PL measurements showed a broad emission band in the 380 – 800 nm range, centred at 481 nm. ZnO NPs thin film yielded relatively more intense photoluminescence spectra than the ZnO NPs powder. The intrinsic point defects and defect level transitions responsible for the broad emission are discussed.

Achieving control over the morphology of conjugated polymer (CP) blends at nanoscale is crucial for enhancing their performances in diverse organic optoelectronic devices, including thin film transistors, photovoltaics, and light emitting diodes. However, the complex CP chemical structures and intramolecular interactions often make such control difficult to implement. We demonstrate here that cooperative combination of non-covalent interactions, including hydrogen bonding, coordination interactions, and π-π interactions, etc., can be used to effectively define the morphology of CP blend films, in particular being able to achieve accurate spatial arrangement of nanoparticles within CP nanostructures. Through UV-vis absorption spectroscopy and transmission electron microscopy, we show strong attachment of fullerene molecules, CdSe quantum dots, and iron oxide nanoparticles, onto well-defined CP nanofibers. The resulting core/shell hybrid nanofibers exhibit well-defined donor/acceptor interface when employed in photovoltaic devices, which also contributes to enhanced charge separation and transport. These findings provide a facile new methodology of improving CP/nanoparticle interfacial properties and controlling blend morphology. The generality of this methodology demonstrated in current studies points to a new way of designing hybrid materials based on organic polymers and inorganic nanoparticles towards applications in modern electronic devices.

In addition to student assessment, curriculum assessment is a critical element to any pedagogy. It helps the educator assess the teaching of concepts, determine what may be lacking, and make changes for continual improvement. Meaningful assessment can be complicated when disciplines converge or when new approaches are implemented. To facilitate this, we present a network-based visualization schema to represent a materials informatics curriculum that combines materials science and data science concepts. We analyze the curriculum using network representations and relevant concepts from graph theory. This reveals established connections, linkages between materials science and data science, and the extent to which different concepts are connected. We also describe how some materials science topics are introduced from a data perspective, and present an illustrative case study from the curriculum.

A synapse is a junction between two biological neurons, and the strength, or weight of the synapse, determines the communication strength between the neurons. Building a neuromorphic (i.e. neuron isomorphic) computing architecture, inspired by a biological network or brain, requires many engineered synapses. Furthermore, recent investigation in neuromorphic photonics, i.e. neuromorphic architectures on photonics platforms, have garnered much interest to enable high-bandwidth, low-latency, low-energy applications of neural networks in machine learning and neuromorphic computing. We propose a graphene-based synapse model as a core element to enable large-scale photonic neural networks based on on-chip multiwavelength techniques. This device consists of an electro-absorption modulator embedded in a microring resonator. We also introduce an encoding protocol that allows for the representation of synaptic weights on our photonic device with 15.7 bits of resolution using current control hardware. Recent work has suggested that graphene-based modulators could operate in excess of 100 GHz. Combined with our work, such a graphene-based synapse could enable applications for ultrafast and online learning.

There exists a need for an innovative reconstructive approach for breast reconstruction, tackling current drawbacks and limitations present in the clinic. In this respect, adipose tissue engineering could offer a promising alternative. We have previously shown that methacrylamide-functionalized gelatin scaffolds are suitable to support the adhesion of adipose tissue-derived stem cells as well as their subsequent differentiation into the adipogenic lineage. The current paper aims to compare different techniques to produce such scaffolds including direct versus indirect 3D printing. Extrusion-based (direct) 3D printing was compared to indirect 3D printing exploiting a polylactic acid (PLA) sacrificial mould, thereby focussing on the physico-chemical characteristics of the obtained scaffolds. The results indicate that similar properties can be achieved irrespective of the technique applied. It can therefore be concluded that indirect 3D printing could offer some benefits over direct additive manufacturing (AM) as a more complex design can be created while materials that were previously unsuited for direct printing because of limitations associated with their characteristics (e.g. low viscosity), could potentially be applied as starting materials for indirect 3D printing to generate porous constructs with full control over their design.

The feasibility of using kimberlite tailings as aggregates in concrete was assessed. Compressive strength and selected durability tests were carried out on concretes made using various replacement levels (0, 40, 60 and 100%) fine and/or coarse blended crushed andesite and kimberlite tailings as aggregates. A w/b ratio of 0.50 and a CEM I 52.5R were used. The results show that the kimberlite tailings as aggregates have a relatively high water demand which was manifested as a reduction in workability of the fresh concretes with kimberlite tailings as a proportion of either fine and/or coarse aggregates. The results also showed that the use of the kimberlite tailings as a proportion of either fine or coarse aggregates in concrete resulted in a decrease in both compressive strength and durability properties viz water sorptivity and oxygen permeability. This was partly attributed to the low workability of the concretes which is known to limit the degree of compaction of fresh concrete. It is envisaged that careful concrete mix proportioning including the use of admixtures and pre-wetting of the aggregates can be used to offset the negative effects of high water demand of the kimberlite aggregates.

Historically, the enthalpy is the criterion for oxide materials discovery and design. In this regime, highly controlled thin film epitaxy can be leveraged to manifest bulk and interfacial phases that are non-existent in bulk equilibrium phase diagrams. With the recent discovery of entropy-stabilized oxides, entropy and disorder engineering has been realized as an orthogonal approach. This has led to the nucleation and rapid growth of research on high-entropy oxides – multicomponent oxides where the configurational entropy is large but its contribution to its stabilization need not be significant or is currently unknown. From current research, it is clear that entropy enhances the chemical solubility of species and can realize new stereochemical configurations which has led to the rapid discovery of new phases and compositions. The research has expanded beyond studies to understand the role of entropy in stabilization and realization of new crystal structures to now include physical properties and the roles of local and global disorder. Here, key observations made regarding the dielectric and magnetic properties are reviewed. These materials have recently been observed to display concerted symmetry breaking, metal-insulator transitions, and magnetism, paving the way for engineering of these and potentially other functional phenomena. Excitingly, the disorder in these oxides allows for new interplay between spin, orbital, charge, and lattice degrees of freedom to design the physical behavior. We also provide a perspective on the state of the field and prospects for entropic oxide materials in applications considering their unique characteristics.

Inorganic perovskite photodetector with chromium interdigitated electrodes is investigated. The active material is a solution processed CsPbI3 synthesized by one step deposition. The α-phase of this material is unstable at room temperature and it converts to the δ-phase at temperatures below 320°C. The stabilization of the α-phase was conducted in nitrogen environment by adding 5% weight ratio of polyethylene oxide to the equimolar mixture of PbI2 and CsI in dimethyl sulfoxide. The absorbance spectrum of the CsPbI3 with polyethylene oxide showed the emergence of a second peak at ∼ 690 nm related to the α-phase in addition to the peak at 420 nm of the δ phase. The peak in the visible range was also observed in the μ-photoluminescence spectrum at 690 nm. The interdigital structure was prepared by photolithography method to deposit 80 nm of chromium interdigitated electrodes on glass substrate with 10 μm channel width. The detector's on/off ratio and the detectivity were calculated from the current voltage curve under 100 mW/cm2 to be 9.64×103 and 9.2×109 Jones respectively.

Bio-composite materials with optimal mechanical and structural properties and capability of cell differentiation are crucial for tissue engineering. Synthetic collagen proteins with lengths of approximately 10 nanometers, along with natural spider silk proteins provide an opportunity for development of an optimal biomaterial for scaffolding applications in tissue engineering. This combines unique mechanical, structural and biological properties of two of the nature’s best polymer proteins, albeit the collagen used in the present work is of the synthetic nature, it mimics the properties and advantages of natural collagen itself. In the present work, we study the binding capability of these proteins at a molecular level via molecular dynamics modeling. Spider silk and synthetic collagen protein molecular models in biophysical saline conditions under standard pressure and temperature are investigated to understand if natural binding occurs between the two without any other external factors. An initial minimum separation of 10 angstroms between the proteins was used. Binding was observed between the two proteins throughout the dynamic simulation of 100 nanoseconds. The radius of gyration and minimum distance between the proteins shows a decreasing separation between the two proteins until a stable distance of 2.5 nanometers and 0.2 nanometers respectively, is achieved. Binding is further observed between the proteins via formation of strong and stable hydrogen bonds. A hydrogen bond between collagen Proline-31 and silk Serine-96 was observed to be the most stable and frequent bond between the single collagen and silk system. Results clearly indicate a self-assembly behavior of these two systems illustrating their potential as a biomaterial for tissue engineering.

The prepared silver/chitosan nanocomposite and chitosan nanoparticles in this study may demonstrate the potential in optimizing the minimum amount required to achieve complete inactivation of various Coliform bacteria in Nile water. Chitosan nanoparticles were prepared based on the ionic gelation of the prepared chitosan and silver nanoparticles were reduced by Solenostemma Argel extract. Finally, chitosan silver-loaded nanoparticles were prepared by dispersing silver nanoparticles onto the chitosan nanoparticles. The SEM images exhibited a diameter range of 10 nm–30 nm for both of the fabricated silver nanoparticles and chitosan nanoparticles. The UV-Vis analysis confirmed the formation of Ag nanoparticles by the appearance of the characteristic peak at 410 nm. The antibacterial activity of chitosan nanoparticles and silver-loaded nanoparticles was evaluated against the Coliform bacteria. Results show an improvement in the inhibition of the growth of various bacteria tested when silver nanoparticles were introduced which was (0.03g/100ml). Consequently, chitosan silver-loaded nanoparticles could be recommended as an efficient antibacterial material for water disinfection.