Interaction of GaAs with sulfur can be immensely beneficial in reducing the deleterious effect of surface states on recombination attributes. Bonding of sulfur on GaAs is also important for developing novel molecular devices and sensors, where a molecular channel can be connected to GaAs surface via thiol functional group. However, the primary challenge lies in increasing the stability and effectiveness of the sulfur passivated GaAs. We have investigated the effect of single and double step surface passivation of n-GaAs(100) by using the sulfide and fluoride ions. Our single-step passivation involved the use of sulfide and fluoride ions individually. However, the two kinds of double-step passivations were performed by treating the n-GaAs surface. In the first approach GaAs surface was firstly treated with sulfide ions and secondly with fluoride ions, respectively. In the second double step approach GaAs surface was first treated with fluoride ions followed by sulfide ions, respectively. Sulfidation was conducted using the nonaqueous solution of sodium sulfide salt. Whereas the passivation steps with fluoride ion was performed with the aqueous solution of ammonium fluoride. Both sulfidation and fluoridation steps were performed either by dipping the GaAs sample in the desired ionic solution or electrochemically. Photoluminescence was conducted to characterize the relative changes in surface recombination velocity due to the single and double step surface passivation. Photoluminescence study showed that the double-step chemical treatment where GaAs was first treated with fluoride ions followed by the sulfide ions yielded the highest improvement. The time vs. photoluminescence study showed that this double-step passivation exhibited lower degradation rate as compared to widely discussed sulfide ion passivated GaAs surface. We also conducted surface elemental analysis using Rutherford Back Scattering to decipher the near surface chemical changes due to the four passivation methodologies we adopted. The double-step passivations affected the shallower region near GaAs surface as compared to the single step passivations.

The microstructure of Ni-Mg-Al mixed oxides obtained by thermal decomposition of hydrotalcite-like compounds synthesized by a co-precipitation method has been studied by using X-ray diffraction (XRD) and atomic resolution transmission electron microscopy (TEM). XRD patterns revealed the formation of NixMg1-xO (x=0÷1), α-Al2O3 and traces of MgAl2O4 and NiAl2O4 phases. The peaks profile analysis indicated a small grain size, microdeformations and partial overlapping of peaks due to phases with different, but similar interplanar spacings. The microdeformations point out the presence of dislocations and the peaks shift associated with the presence of excess vacancies. The use of atomic resolution TEM made it possible to identify the phases, directly observe dislocations and demonstrate the vacancies excess. Atomic resolution TEM is achieved by applying an Exit Wave Reconstruction procedure with 40 low dose images taken at different defocus. The current results suggest that vacancies of metals are predominant in MgO (NiO) crystals and that vacancies of Oxygen are predominant in Al2O3 crystals.

Different aging heat treatments were performed in a Titanium alloy using as aging media metallic baths in comparison to typical furnace aging. As a first step, a Duplex Aging (DA) consisted of solubilization followed by quenching to room temperature after aging heat treatment in different metallic baths (Zn, Sn and Bi). A second procedure was Alternative Aging (AA) which consisted of solubilization and direct aging inside three different aforementioned baths. Microstructural aging variations begins at half hour until 30 h at 550°C inside metallic bath of Zn, Sn or Bi. Both kinds of aging promoted a microstructural variation and so on microhardness values. Microstructural analysis by Optical Microscopy showed a structural refinement after AA treatment. The highest hardness value of 375 HVN was achieved in Alternative Aging with Zn bath, which was found to be dependent on laminar α phase refining. Moreover, after AA treatment for 0.5, 1, 2, 3, 4, 10 and 30 h at 550°C in the metallic bath of Zn and Sn, the results indicated similar hardness values in different times, resulting in the fastest kinetic for Sn metallic bath at 2 h compared to that 4 h in Zn metallic bath. The observed increase in micro-hardness is not very attractive, it is recommended to use large aging times in order to stabilize final spacing of microstructural features in AA treatment.

From the early eighth century CE Byzantine shops next to the Synagogue and Bath-Gymnasium Complex at Sardis, Turkey, were excavated from 1958 to 1969 more than 50 pounds, or about 350 panes of transparent flat glass sheets interpreted as window glass. Examination using optical microscopy showed little variation in size, shape, thickness, edge shape, tool marks, bubble and cord elongation and alignment. Microstructural and compositional variation of weathered surfaces and unweathered cross sections were studied using scanning electron microscopy with energy dispersive x-ray analysis (SEM-EDS). Differential thermal analysis (DTA) was used to determine glass transition temperature range. Three traditional window-forming methods have been described in the glass technology literature: crown, plate and cylinder. The Sardis glass is most similar to criteria expected for cylinder glass, but significant differences were documented. Consistently patterned characteristics evidence a developed technological practice. Replicative tests were conducted using various forming sequences. Wooden and ceramic two-piece molds were made to overblow one or both ends, and hot glass threads were used to thermal shock the cylinder ends and to make a vertical crack that allowed opening during a reheating and slumping operation. These reconstructed methods fit the observed microstructural and macrostructural characteristics of the glass sheets. Analysis of glass manufacturing methods in antiquity contribute to the historical knowledge of craft practices and to the interpretation of industrial debris excavated at markets and industrial workshops.

Arc welding processes such Gas Tungsten (GTAW), Gas Metal (GMAW) and Submerged Arc (SAW) are typically used in order to produce a weld joint in stainless steels (SS). However, welding thermal cycle generates a sensitization by formation of chromium carbides. In addition, the heat affected zone (HAZ) is also susceptible to sensitization and fracture of the weldment. Weld bead geometric parameters such depth penetration, fusion zone (FZ) width and size of HAZ are mainly determined by welding operation parameters. This research work studies the influence of welding current, welding speed and arc gap on the width and grain size in the HAZ produced by a single pass of autogenous GTAW process applied to a plate butt-welded joint of AISI 304 SS. The welded specimens were prepared for analysis by light optical (LOM) and scanning electron (SEM) microscopies to identify the interfaces between FZ-HAZ and base material as well as the grain growth in the HAZ. Adams equation for 2-D heat distribution was used to estimate theoretically the width of the HAZ. Furthermore, computational simulation which solved a convective-diffusion problem of the volumetric heat applied during the weld pool formation allowed to correlate the thermal gradient and the molten material flow of the FZ with the welding depth penetration, and width and grain size in the HAZ. The results demonstrated that the high heat input generates an important grain growth in the HAZ caused by low heat diffusion in the adjacent material to the fusion line. Welding speed was the main factor in the thermal gradient changes. Simulation results indicate that outward recirculating flow in the molten metal produced by surface tension forces is responsible for the shallow penetration of the autogenous GTAW process. Theoretical and computational estimations of the HAZ are in good agreement with the experimental results.

We have produced plasma activated water (PAW) using air, O2, N2, He and Ar atmospheric pressure dielectric barrier discharge plasma irradiation to deionized water. Then, PAW was kept for 1 hour or 1 day at room temperature to reduce concentrations of short lifetime reactive oxygen species and reactive nitrogen species before supplying to plants. O2, air and N2 PAW induces growth enhancement of plants. For 1 hour PAW supply the longest seedling length after 3 days cultivation is 1.62, 1.38, 1.13, 1.12, and 1.04 times long for air, O2, He, N2, and Ar plasmas compared with the length for thecontrol, whereas for 1 day PAW supply it is 1.52, 1.28, 1.13, 1.10, and 1.08 times long for air, O2, He, N2 and Ar. Therefore, long lifetime reactive oxygen nitrogen species in PAW is effective for the growth enhancement.

To better understand light induced changes in polymeric coatings commonly used to protect metal artifacts, this work details the decomposition of thin (∼100nm) nitrocellulose-based lacquer films on silver, copper, and gold. Samples were exposed to various wavelengths of light including, UVA (∼340nm), UVB (312nm), and UVC (254nm), under controlled temperature and humidity. Decomposition was characterized using reflection absorption spectroscopy (RAS) and monitoring infrared absorbance bands. The loss of NO2 functional groups was observed and the decrease was fit to a simple two step autocatalytic model involving primary and secondary decomposition steps. The decomposition rate under UVC light exposure was rapid and similar for all substrates. Rate constants for the primary and secondary steps were similar in magnitude and only mildly dependent on temperature. For UVB light exposure, all reaction rates were much slower and secondary decomposition was much faster relative to the primary decomposition step. Decomposition under all conditions resulted in the formation of oxidized species with an infrared spectrum similar to that of carboxylic acids.

The present paper examines nanoporous material – carbon fabrics, which is used as electrodes in rechargeable energy storage capacitors (ultracapacitors). The fabrics structure, impurities composition, the influence of impurity types on ultracapacitor characteristics and the influence of thermal treatments on the impurities concentration are studied. The analysis of the ultracapacitor equivalent circuit with the studied material is made and the capacitor charge-discharge characteristics are investigated.

The performed studies resulted in determination of the investigated carbon material structure, determination of impurities composition of carbon material and change of impurities content depending on thermal treatment in vacuum. The optimum temperature range for treatment in vacuum is established. The equivalent circuit of the ultracapacitor is analyzed and its charge-discharge characteristics are investigated. The chosen equivalent circuit makes it possible to estimate the influence of pores different size on the ultracapacitor charge-discharge characteristics that is important for its application in energy storage devices.

Palladium germanide thin films were investigated for infrared plasmonic applications. Palladium thin films were deposited onto amorphous germanium thin films and subsequently annealed at a range of temperatures. X-ray diffraction was used to identify stoichiometry, and Scanning Electron Micrographs, along with Energy Dispersive Spectroscopy (EDS) was used to characterize composition and film quality. Resistivity was also measured for analysis. Complex permittivity spectra were measured from 0.3 to 15 µm using IR ellipsometry. From this, surface plasmon polariton (SPP) characteristics such as propagation length and mode confinement were calculated and used to determine appropriate spectral windows for plasmonic applications with respect to film characteristics. Films were evaluated for use with on-chip plasmonic components.

Off-white water pots have had sustained traditional acceptance for a long period of time in Jodhpur compared to red colored water pots imported from the neighboring Gujarat state. Both types of pots hold 20 liters of potable water. The fluorescence spectroscopy reveals dominance of silica, alumina and iron oxide in red pots from Gujarat whereas off-white pots from Rajasthan also have a slight excess of CaO and MgO. Fourier transform infrared spectroscopy reveals a firing temperature of 800 °C for off-white pots, which is comparatively less than that for red pots. A lower amount of Fe2O3 and higher MgO in off-white compared to red water pots is responsible for the color differentiation. Off-white pots show a better degree of cooling compared to red pots. Better resistance to load was observed in off-white pots compared to red pots. This study may imply influence of hidden techno-functional aspects towards sustainability of off-white pots in Jodhpur, Rajasthan.

For a wide range of bandgaps of solar cell materials, the potential contribution of upconversion materials was calculated and related to various configurations of the solar cell and upconversion layers. Moreover, by comparing these various strategies with the potential of a dual junction tandem cell configuration, a compelling case is made for upconverters.

At idealized 100% conversion efficiency, the upconverter with a single junction cell is more efficient than a dual junction tandem cell. It was also found that a single junction cell with an upconverter that is ‘only’ 80% efficient has a similar efficiency as an ideal dual junction cell. This result shows that upconverters are certainly a route worthwhile to pursue, especially because the single junction cells plus upconverters could have more cost reduction potential than dual junction cell configurations.

Additionally, it was investigated if an upconverter that uses two different photon energies would create a large surplus in efficiency. For a cell band gap of 1.55 eV a theoretical maximum efficiency (here defined as Voc*Isc) of 54.5% was calculated. Although there is a further increase in efficiency compared to converters with a single conversion energy, very careful bandgap tuning with a tolerance < 0.02 eV is required, which makes this system rather sensitive for material and solar spectrum fluctuations and it is suggested that a simple upconverter material is a more favorable strategy.

We show that superlattice (SL) of PbS quantum dots (QD) can be easily prepared by drop casting of colloidal QD solution onto glass substrate and the ordering level can be controlled by the substrate temperature. A QD solution was dropped on glass and dried at 25, 40, 70 and 100°C resulting in formation of different SL structures. X-ray diffractograms (XRD) of deposited films show a set of sharp and intense peaks that are higher order satellites of a unique peak at 1.8 degrees (two theta), which corresponds, using the Bragg’s Law, to an interplanar spacing of 5.3 nm. The mean particles diameter, calculated through the broadening of the (111) peak of PbS using the Scherrer’s formula, were in agreement with the interplanar spacing. Transmission electron microscopy (TEM) measurements were also used to study the SL structure, which showed mainly a face centered cubic (FCC) arrangement of the QD. The photoluminescence (PL) spectrum of QD in the SL showed a shift toward lower energy compared to one in solution. It can be attributed to the fluorescence resonant energy transfer (FRET) between neighbors QD´s. Moreover, we observed greater redshift of PL peak for film with lower drying temperature, suggesting that it has a more organized structure.

The ordering of polarization field of inhomogeneous ferroelectric systems were investigated. We found that these systems exhibit rather complex polarization ordering behaviors with the coexistence of polar and toroidal ordering, and particularly, a novel and tunable polar-toroidal phase transformation under external mechanical, electrical or thermal fields. Accompanying with this polar-toroidal phase transformation, there is a large change of polarization and strain. As a result, large eletromechanical and thermomechanical performance can be achieved in these systems. The polar/toroidal phase boundaries can be regarded a new kind of morphotropic phase boundary (MPB). The polar-toroidal phase transformation in nanoscale ferroelectric systems should provide us a novel strategy to develop energy conversion nanodevices.

Types of melter feed materials affect glass production rates. This study focuses on the effects of alumina sources on melting behavior of high-alumina high-level-waste melter feeds containing different alumina sources, namely, gibbsite, boehmite, and corundum. The heat flow from the glass melt to the cold cap, a floating layer of the reacting feed, is partially hindered by a foam layer at the bottom of the cold cap. Volume expansion tests and thermoanalytical methods revealed that a slow-melting feed with corundum foamed extensively, whereas a fast-melting feed with boehmite had a low reaction heat and produced less stable foam. The foam thickness, a critical factor for the rate of melting, estimated using the relationship between the heat conductivity and foam porosity was in reasonable agreement with experimental observation.

Ni-Zr alloy thin films were processed by DC magnetron sputtering of high purity Ni and Zr targets in ultrahigh vacuum at ambient temperature, with the substrate being subjected to either 0 V or -60 V bias. Some of the as-deposited films were annealed in vacuum at 700°C for 1 h. Surface profilometer and atomic force microscope were used to measure the film thickness and surface roughness, respectively. X-ray diffraction and cross-sectional TEM analysis have shown dispersion of nano-sized Ni3Zr dispersed in nanocrystalline Ni matrix. Nano-indentation and scratch tests conducted at 2 mN load have shown variation of hardness, Young′s modulus, scratch resistance, and coefficient of friction with substrate bias and annealing due to changes in grain size and surface roughness.

In recent years, tissue engineering has been utilized as an alternative approach to organ transplantation. Success rate of tissue regeneration influenced by the biomaterials, cell sources, growth factors and scaffold fabrication. Design and precise fabrication of scaffolds are required to support cells to expand and migrate to 3D environment. Common scaffold fabrication techniques use heat, adhesives, molds or light. In this research, “inverse-photolithography” which is a light based fabrication technique was used to generate the scaffolds. In order to control the interior architecture of the scaffold “a single vertical strut” and “a y-shape” were fabricated with the 3D printer by using the dissolvable filament. Then, the strut and the y-shape were immersed into the photo-curable solution which is poly(ethylene glycol) diacrylate (PEGDA) and photo-initiator mixture. UV light with the 365nm wavelength was placed up-side down under the solution. Photo-curable mixture was exposed to the UV light for 3 minutes to cure the entire scaffold. Solidified scaffold with the strut and y-shape inside was kept in the limonene solution. Limonene penetrated through the open ended strut and y-shape and it dissolved the 3D printed strut and y-shape away leaving the fabricated PEGDA based scaffolds. This preliminary research showcases, the 3D scaffolds with the controlled interior design, can be fabricated with the “inverse-photolithography” technique.

At the Savannah River Site (SRS) low activity salt solution is stabilized via encapsulation within a grout termed saltstone. Saltstone is emplaced into large (multi-million gallon) concrete storage facilities referred to as Saltstone Disposal Units (SDUs). Technetium-99 (99Tc) is a long-lived radionuclide contained in the low activity salt waste and subsequently incorporated into the grout waste form: it is considered a significant contributor to risk with respect to the long-term radiation exposure of the environment surrounding the SDUs. In the reducing, high pH environment within the grout, 99Tc is expected to be relatively immobile since it exists in a reduced Tc(IV) oxidation state in the form of sparingly soluble sulfides (TcSx) or hydrated oxides (TcO2.xH2O). However, in the presence of O2 (associated with the future infiltration of air or oxygenated ground waters into the saltstone monolith) it is possible for redox-sensitive Tc(IV) to transition into highly soluble (and mobile) Tc(VII) species, pertechnetate (TcO4-), which is more readily transported to the surrounding environment. Traditional approaches to quantifying the leaching behavior of 99Tc from cementitious matrices have involved partitioning experiments using size-reduced (crushed/ground) saltstone samples, and determination of the 99Tc fraction immobilized by the cementitious solids. Such experiments create artificially high solid-solution contact areas that likely result in higher 99Tc leachate concentrations than would be expected for intact, monolithic samples. In the current study a new technique, termed the Dynamic Leaching Method (DLM), is being used to investigate the 99Tc leaching behavior of monolithic saltstone samples. The data derived using this technique is intended to inform the SRS Saltstone Disposal Facility (SDF) Performance Assessment (PA) which models the long-term transport of radionuclides from the SDUs to the environment. The DLM utilizes a flexible-wall permeameter to achieve saturated leaching under an elevated hydraulic gradient in an effort to simulate the transport of groundwater through saltstone. Initial findings indicate that the 99Tc concentrations in the leachate are on the order of 1E-08 mol/L which suggests that the saltstone leaching behavior is controlled by the solubility of TcO2.xH2O compounds.

Chemically exfoliated two-dimensional (2D) materials have shown promise in a variety of applications such as thin film transistors and photovoltaic devices. Here, we present a scalable method for preparing black phosphorus membranes via direct liquid-phase exfoliation of the bulk crystal in organic solvents. The black phosphorus sheets are characterized by Raman and Photoluminescence (PL) spectroscopy, and optical microscopy. The properties of these chemically exfoliated black phosphorus was compared to mechanically exfoliated nanomembranes. The liquid-phase exfoliation nonetheless yields the potential for large-area scalability. Our results highlight the important aspects of forming solution dispersions of 2D black phosphorus which can subsequently be the stepping stone for future work on the ink-jet printing of such dispersions over a wide range of substrates.

As the global populations grow, water demand and pollution of water resources will increase. As a consequence, water borne disease outbreaks are on the rise and current disinfection methods have been shown to be ineffective in inactivating all pathogens during water treatment. Aluminum oxide nanoparticles (Al2O3 NPs) have been shown to poses antimicrobial properties. Also, Al2O3 has high thermal and chemical stability, which makes these NPs an excellent candidate for water treatment applications. Thus, the objective of this work is to assess the bactericidal properties of Al2O3 NPs synthesized using a polyol-based process in presence of polyvinylpyrrolidone (PVP). For practical applications nanoparticles must be immobilized in a medium to ensure that particles are not dispersed into the treated water. For this reason, synthesized nanoparticles were dispersed in electrospun polyacrylonitrile (PAN) membranes to also evaluate the bacterial removal capacity. X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR) analysis suggests that synthesized nanoparticles are γ-Al2O3 after annealing at 800°C for 6 hours. Scanning Electron Microscopy (SEM) characterization was used to determine the morphology and size of synthesized nanoparticles. Composite electrospun membranes were also characterized by XRD, FT-IR, and SEM. The bactericide activity of the synthesized γ-Al2O3 NPs and commercially available Al2O3 particles was evaluated by the disc diffusion method against E. coli bacteria. Also, Al2O3-PAN composite electrospun membranes bacterial filtration capacity was tested. Both synthesized and industrially produced particles exhibited antibacterial activity against E. coli, but polyol-based synthesized nanoparticles demonstrated better bactericide properties. The bacterial removal capacity of PAN and PAN/Al2O3 fibers was comparable to that of paper filters.

Magnetic bioseparation is an important area of biotechnology. Various techniques are used with a wide range of possible applications in bioscience research. Magnetic micro- or nanospheres can be functionalized with appropriate ligands, such as antibodies, with a high affinity to the target, like cells, bacteria or DNA/RNA. In order to realize magnets with efficient separation capabilities, it is important to have a strong force FM acting on the magnetic bodies. FM is proportional to the product of the magnetic field and the field gradient. Many permanent magnets on the market have large magnetic fields, but relatively weak field gradients. GIAMAG magnets have unique and patented designs that produce both very large magnetic fields and high field gradients, resulting in the most forceful magnetic separators available on the market.