We report experimental and computational studies of Ba doping for Cs in Cs2TiNb6O18, a material with potential to be an exceptional ceramic waste form for Cs sequestration. Three co-doping (simultaneous metal reduction for charge balance of Ba2+ for Cs+) schemes have been experimentally tested: Ti4+ for Nb5+, Ti3+ for Ti4+ and Nb4+ for Nb5+. Unfortunately, none showed conclusively that the co-substitution was successful. Atomistic modelling was then performed on all three schemes using novel potentials to assess the energetic feasibility, from these the most favourable scenario is reduction of Nb5+ to Nb4+.

Ancient Chinese bronzes are precious cultural relics. Their surfaces are often severely damaged by dynamic changes in the external environment, both before and after they are unearthed. Therefore, scientific research has been required to preserve these treasures. In recent years, along with the development of modern science and technology, innovative instrumental analytical techniques have become indispensable tools to study corrosion phenomena as well as to evaluate post-excavation conservation techniques. In this paper, we present an overview of bronze corrosion processes in various environments, including analysis of the types of corrosion, mechanisms of formation and factors that influence bronze corrosion products. In addition, we compare the characteristics of corrosion products that have formed on archaeological sites, in tombs, and in museums. Lastly, we introduce some novel techniques for bronze protection, and we propose the focus for future research. Our expectation is that this review will provide a scientific basis for bronze preservation.

In this study the improvement in thermal stability of optical properties of InAs submonolayer quantum dot (SML QD) heterostructures is observed through incorporation of symmetric AlGaAs barrier layers. Low temperature photoluminescence (PL) spectra shows blue shift with less full width at half maxima, ascribe to the assimilation of AlGaAs barrier layers. The sample with confinement enhancing barrier shows the highest ground to ground transition energy with the lowest dot size distribution. Ex situ annealing of as grown samples, followed by PL analysis, confirms the improvement in thermal stability of optical behavior. For the samples with symmetric AlGaAs layer, annealing at higher temperatures under an inert condition can not change the downward transition energy effectively, whereas normal DWELL structures exhibits significant blue shift for the same.

In this work we have investigated, by fully atomistic reactive (force field ReaxFF) molecular dynamics simulations, some aspects of impact dynamics of water nanodroplets on graphdiyne-like membranes. We simulated graphdiyne-supported membranes impacted by nanodroplets at different velocities (from 100 up to 1500 m/s). The results show that due to the graphdiyne porous and elastic structure, the droplets present an impact dynamics very complex in relation to the ones observed for graphene membranes. Under impact the droplets spread over the surface with a maximum contact radius proportional to the impact velocity. Depending on the energy impact value, a number of water molecules were able to percolate the nanopore sheets. However, even in these cases the droplet shape is preserved and the main differences between the different impact velocities cases reside on the splashing pattern at the maximum spreading.

Failure of metallic materials due to plastic and/or creep deformation occur by the emergence of necking, microvoids, and cracks at heterogeneities in the material microstructure. While many traditional deformation modeling approaches have difficulty capturing these emergent phenomena, the discrete element method (DEM) has proven effective for the simulation of materials whose properties and response vary over multiple spatial scales, e.g., bulk granular materials. The DEM framework inherently provides a mesoscale simulation approach that can be used to model macroscopic response of a microscopically diverse system. DEM naturally captures the heterogeneity and geometric frustration inherent to deformation processes. While DEM has recently been adapted successfully for modeling the fracture of brittle solids, to date it has not been used for simulating metal deformation. In this paper, we present our progress in reformulating DEM to model the key elastic and plastic deformation characteristics of FCC polycrystals to create an entirely new crystal plasticity modeling methodology well-suited for the incorporation of heterogeneities and simulation of emergent phenomena.

A modification of the growth structure of Eu-doped GaN (GaN:Eu) from a monolayer to a multilayer structure (MLS) consisting of alternating GaN and GaN:Eu, was shown to enhance the emission properties. Similarly, lowering the growth temperature of the GaN:Eu to 960°C nearly doubled the photoluminescence emission intensity, and also enhanced device performance. Hence, to design a higher power GaN:Eu red LED, a multilayer structure consisting of 40 pairs of alternating GaN and GaN:Eu was grown at 960°C. This combination resulted in the fabrication of an LED with a maximum output power of 110 μW, which is 5.8 times more output power per GaN:Eu layer thickness as compared to the best previously reported device. Moreover, it was found that the MLS sample grown at 960°C maintained a high crystal quality with low surface roughness, which enabled an increase in the number of pairs from 40 pairs to 100 pairs. An MLS-LED consisting of 100 pairs of alternating GaN/GaN:Eu layers was successfully fabricated, and had a maximum output power of 375 μW with an external quantum efficiency of 4.6%. These are the highest values reported for this system.

In this work, a planar heterojunction superstrate n-i-p device based on Zn(O,S) electron transport layer and CsPbI2Br absorber material at 1.93 eV bandgap is presented. The CsPbI2Br films are deposited using a 2-step atmospheric solution deposition process and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis spectroscopy and photoluminescence (PL). Best device with an efficiency of 12.34 % and 11.94% in reverse and forward scans respectively and stabilized power output of 12.14 mW/cm2 has been demonstrated via atmospheric solution processing with minimal hysteresis between forward and reverse scans. The devices show voltage dependent current collection as well as light-dark crossover in forward bias. Light soaking tests at 65 °C and 1-sun at Voc, resulted in open-circuit voltage and fill-factor degradation. Electroluminescence (EL) after 100 hours of light soaking shows a reduction in overall EL intensity as well a shift in emission to lower wavelength. The devices exhibit a positive temperature coefficient of about 0.14 %/°C. It is found that Zn(O,S) is a viable alternative electron transport layer to replace TiO2. By replacing methylammonium cation with cesium and addition of Br has improved the stability of the perovskite phase.

In today’s technology, organ transplantation is found very challenging as it is not easy to find the right donor organ in a short period of time. In the last several decades, tissue engineering was rapidly developed to be used as an alternative approach to the organ transplantation. Tissue engineering aims to regenerate the tissues and also organs to help patients who waits for the organ transplantation. Recent research showed that in order to regenerate the tissues, cells must be seeded onto the 3D artificial laboratory fabricated matrices called scaffolds. If cells show healthy growth within the scaffolds, they can be implanted to the injured tissue to do the regeneration. One of the biggest limitation that reduces the success rate of tissue regeneration is the fabrication of accurate thick 3D scaffolds. In this research “maskless photolithography” was used to fabricate the scaffolds. Experiment setup consist of digital micro-mirror devices (DMD) (Texas Instruments, DLi4120), optical lens sets, UV light source (DYMAX, BlueWave 200) and PEGDA which is a liquid form photo-curable solution. In this method, scaffolds are fabricated in layer-by-layer fashion to control the interior architecture of the scaffolds. Working principles of the maskless photolithography is, first layer shape is designed with AutoCAD and the designed image is uploaded to the DMD as a bitmap file. DMD consists of hundreds of tiny micro-mirrors. When the UV light is turned on and irradiated the DMD, depending on the micro-mirrors’ angles, UV light is selectively reflected to the low percentage Polyethylene (glycol) Diacrylate (PEGDA) photo-curable solution. When UV light penetrates into the PEGDA, only the illuminated part is solidified and non-illuminated area still remains in the liquid phase. In this research, scaffolds were fabricated in three layers. First layer and the last layer are solid layers and y-shape open structure was sandwiched between these layers. After the first layer is fabricated with DMD, a “y-shape” structure was fabricated with the 3D printer by using the dissolvable filament. Then, it was placed onto the first solid layer and covered with fresh high percentage PEGDA solution. UV light was reflected to the PEGDA solution and solidified to make the second and third layers. After the scaffold was fabricated, it is dipped into the limonene solution to dissolve the y-shape away. Our results show that thick scaffolds can be fabricated in layer-by-layer fashion with “maskless photolithography”. Since the UV light is stable and does not move onto the PEGDA, entire scaffold can be fabricated in one single UV shot which makes the process faster than the current fabrication techniques.

We report a robust method by which colloidal PbS nanosheets can be synthesized with nearly 100% success rate. It is achieved by replacing the lead acetate by lead oxide for preparation of the lead precursor. Acetic acid either injected externally or produced during the reaction can significantly affect the growth of the nanosheets. The existence of water in the reaction solution makes the nanosheets smaller in lateral size while the purity of trioctylphosphine has no significant effect on the nanosheet growth.

Polysilicon complementary metal oxide semiconductor (CMOS) thin film transistors (TFTs) are fabricated on large area, flexible stainless steel foils using novel ink depositions within a hybrid printed/conventional process flow. A self-aligned top gate TFT structure is realized with an additive materials approach to substitute the use of high capital cost ion implantation and lithography processes. Polyhydrosilane-based silicon ink is coated and laser crystallized to form the polysilicon channel. Semiconductor grade P-type and N-type unique dopant ink formulations are screen printed and combined with thermal drive in and activation to form self-aligned doped source and drain regions. A high refractory top gate material is chosen for its process compatibility with printed dopants, chemical resistance, and work function. Steel foil substrates are fully encapsulated to allow for high temperature processing. The resultant materials set and process flow enables TFT electrical characteristics with NMOS and PMOS mobilities exceeding 120 cm2/Vs and 60 cm2/Vs, respectively. On/Off ratios are >107. Reproducibility, uniformity, and reliability data in a production environmental is shown to demonstrate high volume, high throughput manufacturability. The device characteristics and scheme enable NFC (13.56MHz) capable circuits for use in flexible NFC and display-based smart labels and packaging.

This contribution reports the synthesis and characterization of La-based perovskites which can be used for the production of syngas via solar thermochemical splitting of H2O/CO2. The La-based perovskites were synthesized using a solution combustion synthesis approach. The derived perovskites were analyzed using powder X-ray diffractometer (PXRD), BET surface area analyzer (BET), and scanning/transmission electron microscope (SEM/TEM). The results associated with the synthesis and characterization of La-based perovskites is reported in detail.

We have studied earthen plasters and wall materials from three ancient Native American sites in the American Southwest that include a twelfth-century, subterranean kiva used for textile production in Natural Bridges National Monument (Utah), a thirteenth-century, defensive, cliff dwelling at Montezuma Castle (Arizona), and a mid-fourteenth-century, puddled earth Great House at Casa Grande National Monument (Arizona). In each case, the data collected has been used to develop long-term preservation strategies and monitoring plans for each site. To understand the conservation issues, earthen materials were analyzed. Characterization included examination of BSE-SEM micrographs of polished thin sections prepared from a total of 36 samples from the three sites, and XRD of twelve samples. Research goals included: 1) determining the microstructure, micro-composition, porosity, mineralogy of aggregates and phases in the binding matrix for each sample; 2) reconstructing plaster technologies and their variation within and between sites, including material selection, preparation and application sequences, and; 3) identifying principal deterioration conditions and processes. Our findings support the idea that plaster materials were collected locally and manipulated to optimize their performance to suit the unique site conditions and needs of the ancient people using the structures.

In the context of management of the wastes arising from the reprocessing of spent nuclear fuel, studies have been conducted into the solvent extraction kinetics of lanthanide fission products by TODGA and the effects of solvent phase acidity on the effectiveness of this organic extractant molecule. In this study we observe an increase in organic phase viscosity increasing acidity and, potentially by consequence, that the rate of cerium extraction is summarily decreased.

The aim of this research is to ameliorate the dispersion of pristine and functionalized Carbon Nanotubes (CNTs) into polystyrene with hydroxyl end groups (PSOH) matrices using low magnetic fields. The Multi-Walled Carbon Nanotubes (MWCNTs) were synthesized by chemical vapor deposition (CVD) using benzene as carbon source; to produce CNTs with and without functional groups two catalysts were used (stainless steel and ferrocene). The obtained nanotubes contained iron nanoparticles inside. PSOH were synthesized using styrene as monomer, azobisisobutyronitrile as initiator and 2-MeOH as chain transfer agent. The MWCNTs-PSOH matrices were formed using 1.6 wt % of carbon nanotubes into PSOH and ultrasonic mixing for 30 min. The mixing materials were poured into containers and dry at room temperature. While the material was drying, constant magnetic fields of 0.24 T were being applied for 50 min. The MWCNTs-PSOH composites were analysed by SEM, FTIR and Raman spectroscopy. SEM micrographs showed that MWCNTs without functional groups were incorporated in the middle of PSOH. The MWCNTs functionalized perform differently; a better dispersion through the entire polymer matrix was achieved, because the polymer embedded the CNTs. FTIR and Raman spectroscopy showed chemical interaction between PSOH and MWCNTs functionalized. The CNTs dispersion into PSOH was ameliorated through the use of low magnetic fields and functionalization.

There are growing interests on magnetic nanowires, due to their potential applications in magnetic sensors and recording devices. In this work, we report a comparative ab-initio study based on the Density Functional Theory (DFT) of Ni x Fe1-x nanowire periodic arrays by using atomic-orbital and plane-wave basis respectively through DMol3 and CASTEP codes. After performing the geometry optimization, we calculate the spin-polarized electronic density of states, average interatomic distance, and magnetic moments. For pure Ni nanowires (x = 1, the dependence of the magnetic moment obtained from CASTEP calculations on the cutoff energy, as well as that from DMol3 on the thermal smearing parameter is analyzed in detail. Both ab-initio calculations predict close magnetic moments for each x, being slightly larger those of DMol3 obtained with significantly less computing cost. Finally, these DFT results are compared with experimental data and a good agreement is observed.

Herein, we demonstrate a facile, rapid, and scalable method to fabricate polymer-based gratings for surface-enhanced Raman spectroscopy (SERS) sensors. To accomplish this, epoxy nanostripe arrays on silicon substrates were prepared using thermal annealing and UV-cross-linking. After preparation of the nanostripe arrays, the surface was briefly treated with oxygen plasma, which decreased the surface energy and enabled the growth of AgNPs on the polymer surface using a simple, low-cost, aqueous-based synthesis procedure. The SERS substrates exhibited a detection limit of ∼1 pM using rhodamine 6G (R6G). In addition, preliminary work with E. coli DH5 showed that the nanoimprinted substrates can be used to obtain Raman spectra of washed bacteria cells.

Cryptomelane type manganese dioxides (α-MnO2, OMS-2) are interesting potential cathode materials due to the ability of their one dimensional (1D) tunnels to reversibly host various cations including Li+ and an accessible stable 3+/4+ redox couple. Here, we synthesized metal cation free OMS-2 materials where the tunnels were occupied by only water and hydronium ions. Water was subsequently removed from the tunnels. Cation free OMS-2 and Dry-OMS-2 were used as cathodes in Li based batteries to investigate the role of tunnel water on their electrochemistry. The initial discharge capacity was higher for Dry-OMS-2 (252 mAh/g) compared to OMS-2 (194 mAh/g), however, after 100 cycles Dry-OMS-2 and OMS-2 delivered 137 mAh/g and 134 mAh/g, respectively. Li+ ion diffusion was more facile for Dry-OMS as evidenced by rate capability, at 400 mA/g. Dry-OMS-2 delivered 135mAh/g whereas OMS-2 delivered ∼115 mAh/g. This first report of the impact of tunnel water on the electrochemistry of OMS-2 type materials demonstrates that the presence of tunnel water in OMS-2 type materials negatively impacts the electrochemistry.

Aluminum-Graphite composites were prepared from pure aluminum and natural graphite the mixture was processed by the mechanical milling (MM) technique. The microstructural characteristics of prepared composites were investigated by X-rays diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM). The mechanical response of samples was evaluated by compression and hardness tests. To obtain solid samples from milled powders we used an alternative sintering process based on induction heating. Although this method is frequently used for refractory ceramics fabrication (>1500°C), it has not been properly evaluated for materials processing at low temperature (<500°C). This work presents a comparative study of Al-Gr composites sintered by using two routes: conventional pressure-less and high frequency induction heating. After the inductive sintering, is noticeable a pronounced reduction of porosity and increase on the mechanical response of induction sintered specimens, compared with the processed by conventional route. Also, yield strength and hardness increases with graphite addition and induction sintering reaching an increase of 50 and 90%, respectively (compared with an Alp-2h blank).

A preliminary investigation of the synthesis and characterization of simulant ‘lava-like’ fuel containing materials (LFCM), as low activity analogues of LFCM produced by the melt down of Chernobyl Unit 4. Simulant materials were synthesized by melting batched reagents in a tube furnace at 1500 °C, under reducing atmosphere with controlled cooling to room temperature, to simulate conditions of lava formation. Characterization using XRD and SEM-EDX identified several crystalline phases including ZrO2, UOx and solid solutions with spherical metal particles encapsulated by a glassy matrix. The UOX and ZrO2 phase morphology was very diverse comprising of fused crystals to dendritic crystallites from the crystallization of uranium initially dissolved in the glass phase. This project aims to develop simulant LFCM to assess the durability of Chernobyl lavas and to determine the rate of dissolution, behavior and evolution of these materials under shelter conditions.

The ground state properties of pure Ti with α, β and ω structures and of the binary Ti-xV(x=5‒30) at.% alloys with β and ω structures were calculated by first-principles method based on density functional theory, and subsequently the energy landscape of the displacive phase transition of β to ω were determined. The calculated results show that the energy barrier appears for the displacive phase transition of β to ω in Ti-(15‒30) at.% V alloys at 300 K, but does not at 0 K. The energy barriers increase monotonously with increase of the temperature and the V content. These results can explain the formation of athermal ω phase and shear-assisted β to ω transition observed in as-quenched Ti-V base alloys.