Single-phase monazite-type ceramics are discussed as waste forms for the safe disposal of surplus plutonium or separated minor actinides. To derive a fundamental understanding of the long-term stability of these materials under repository relevant conditions, the dissolution kinetics of synthetic lanthanum monazite (LaPO4) were studied in dynamic dissolution experiments in the temperature range from 50 to 90°C under acidic conditions. The surface area normalised dissolution rates increased with temperature from 3.2·10-5 g m-2 d-1 at 50°C to 1.8·10-4 g m-2 d-1 at 90°C. The apparent activation energy Ea of the dissolution process was determined to be about 44 kJ mol-1, indicating a predominantly surface reaction controlled dissolution process in this temperature range. From thermodynamic considerations it can be inferred that the dissolution of the LaPO4 ceramics is governed by the dissolution of a thin layer of La-rhabdophane (LaPO4 · 0.667H2O) forming at the monazite surface in low temperature aqueous environments.

Efficient catalysts for the oxygen evolution reaction (OER) are widely applied in fuel cells and rechargeable lithium air batteries. It is desirable but challenging to achieve comparable activity to that of the noble-metal catalyst with non-precious metal catalyst. Highly active Co3O4 thin film electrodes have been successfully synthesized by a rapid one-step flame combustion synthesis method called Reactive Spray Deposition Technology. X-ray diffraction confirms the absence of any impurity phase with this synthesis process. The detailed morphology of the Co3O4 thin film is investigated with scanning electron microscopy and transmission electron microscopy. Cyclic voltammetry is used to investigate the redox activity of Co3+ to Co4+ which is crucial for the OER performance. The as-prepared Co3O4 catalyst demonstrates promising activity for OER, with an overpotential of 399 mV (at 10 mA cm-2) for OER.

The atmospheric pressure plasma sources with a coaxial geometry were used for generation of the radio frequency, microwave and pulsed dc plasmas inside water and aqueous solutions. Pulsed dc plasma generated in ethanol-water mixtures leads to production of the hydrogen-rich synthesis gas with hydrogen content up to 65 %. The effect of various plasma generation regimes on the performance of plasma, on the hydrogen production efficiency and on the hydrogen-rich synthesis gas production was examined. A role of the composition of the ethanol-water mixture was investigated.

In our contribution we present and analyze implementation of the resistive switching structures for logic application based on Zadeh fuzzy logic. Resistive switching structures based on HfOx and TaOx were connected in an anti-serial configuration (complementary resistive switch). The complementary resistive switches integrated into logic circuit for Min-Max function implementation were analyzed using quasi-static voltage sweeps. We have shown that the accuracy of the Min/Max function determination depends on the ratio of the high and low resistivity states of the single switches. Determination of the Min/Max values is relevant only above the threshold voltage of the resistive structures. Reproducibility of the Min/Max function constructed from the resistive switching structures is demonstrated.

Sn clathrates are promising phonon glass, electron crystal materials (PGEC), in which the phonon free paths are short and the electron free paths are long. We analysed the relaxed structure of Sn clathrates using four different Density Funtional Exchange-Correlation functionals. The phonon structures were investigated as a first step in order to determine the phonon contribution to the thermal conductivity. We determined the Seebeck coefficient and electrical conductivity of the clathrate compound and the thermoelectric figure of merit. A glimpse into the dynamics of the system for the evaluation of the thermoelectric and electronic properties is presented.

It is known that tungsten oxide may be reacted with selenium sources to form WSe2 but literature reports include processing steps that involve high temperatures, reducing atmospheres, and/or oxidative pre-treatments of tungsten oxide. In this work, we report a non-vacuum process for the fabrication of compositionally high quality WSe2 thin films via the selenization of tungsten oxide under milder conditions. Tungsten source materials were various hydrated WO3 and WO2.9 compounds that were prepared using chemical solution techniques. Resulting films were selenized using a two-stage heating profile (250 °C for 15 minutes and 550 °C for 30 minutes) under a static argon atmosphere. Effects of the starting tungsten oxide phase on WSe2 formation after single and double selenization cycles were investigated using Raman spectroscopy and X-ray diffraction (XRD). After two selenization cycles, hydrated WO3 was converted to (002)-oriented WSe2 that exhibits well-resolved peaks for E12g and A1g phonon modes. Only a single selenization cycle was required to convert amorphous WO2.9 to WSe2. All selenizations in this work were achieved in non-reducing atmospheres and at lower temperatures and shorter times than any non-laser-assisted processes reported for WO3-to-WSe2 conversions.

The photosynthetic reaction center (RC) is an integral membrane protein that, upon absorption of photons, generates a hole-electron couple with a yield close to one. This energetic state has numerous possible applications in several biotechnological fields given that its lifetime is long enough to allow non-metabolic ancillary redox chemistry to take place. Here we focus on RCs reconstituted in liposomes, formed with sole phospholipids or in blends with other lipids, and show that the electrical charge sitting on the polar head of such hydrophobic molecules does play an important role on the stability of the hole-electron couple. More specifically this study shows that the presence of negative charges in the surrounding of the protein stabilizes the charge-separated state while positive charges have a strong opposite effect.

Materials science is a growing research area in Uruguay. In order to obtain a brief overview of the research done we collected information about research in this field. As a starting point, we searched in the Scopus database for the keywords: affiliation country: “Uruguay” and subject: “Materials Science” (using the “Timbó” platform). We inspected the records and we analyzed them to construct a timeline. The data show that we are in a steady state regime of number of publications that we expect to increase together with the number of students in the area, with the generation of long term policies (grants, funding opportunities), and, if we get involved in a community that promotes this area of interest.

We investigate the origin of satellite features that appear in the high-resolution x-ray absorption spectra measured at the uranium M4 edge in compounds where the uranium atoms are in the U6+ oxidation state. We employ a material-specific Anderson impurity model derived from the electronic structure obtained by the density-functional theory.

The need to improve Education for Sustainable Development (ESD) provision in Greek secondary schools offers opportunities for innovation. This study shows results of applying a more integrated, collaborative and interactive approach, developed by using elements of the Impact of Materials on Society (IMOS) course. The modules and techniques selected for teacher training and classroom implementation are presented and responses from participants are summarised. Positive feedback from the two teacher training activities and two in-class sessions with students demonstrates the potential of this approach. The paper offers evidence that a systems approach to ESD is promising and worthy of further investigation.

Dendritic growth during charging period is one of the main barriers for the rechargeablity of conventional batteries. Additionally this phenomenon hinders the utilization of high energy density metal candidates by limiting the safety and allowable operating condition for these devices. We address the role of square wave pulse on the growth dynamics of dendrites in the continuum scale and large time periods by formulating an analytical criterion. Our dimension-free analysis permits the application our results to a variety of electrochemical systems in diverse scales.

Radioactive waste with widely varying characteristics is generated from the operation and maintenance of nuclear reactors, nuclear fuel cycle facilities, research facilities and medical facilities and the through the use of radioisotopes in industrial applications. The waste needs to be treated and conditioned appropriately to provide wasteforms acceptable for safe storage and disposal. Conditioning of radioactive waste is an important step to prepare waste for long-term storage or disposal and includes the following processes:

• ▪ Immobilization which may or may not also provide volume reduction, including

  • a) Low temperature processes and

  • b) Thermal processes;

• ▪ Containerization for

  • a) Transport,

  • b) Storage, and

  • c) Disposal;

• ▪ Overpacking of primary containers

  • a) Prior to disposal and

  • b) In a disposal facility as part of disposal process.

Conditioning consists of operations that produce a waste package suitable for handling, transportation, storage and/or disposal and may be performed for a variety of reasons including standardization of practices and/or wasteforms, technical requirements for waste stability in relation to a repository design or safety case, technical requirements related to waste transportation, societal preferences, regulatory preferences, etc. This paper gives an overview of recent advances in conditioning of low- and intermediate-level radioactive waste.

The paper is based on the new IAEA Handbook “Conditioning of Low- and Intermediate-Level Liquid, Solidified and Solid Waste” which is one of eight IAEA handbooks intended to provide guidance for evaluating and implementing various characterisation and radioactive waste processing and storage technologies before final disposal

Recently, an epoch-making printing technology called “SuPR-NaP (Surface Photo-Reactive Nanometal Printing)” that allows easy, high-speed, and large-area manufacturing of ultrafine silver wiring patterns has been developed. Here we demonstrate low-voltage operation of organic thin-film transistors (OTFTs) composed of printed source/drain electrodes that are produced by the SuPR-NaP technique. We utilize an ultrathin layer of perfluoropolymer, Cytop, that functions not only as a base layer for producing patterned reactive surface in the SuPR-NaP technique but also as an ultrathin gate dielectric layer of OTFTs. By the use of 22 nm-thick Cytop gate dielectric layer, we successfully operate polycrystalline pentacene OTFTs below 2 V with negligible hysteresis. We also observe the improvement of carrier injection by the surface modification of printed silver electrodes. We discuss that the SuPR-NaP technique allows the production of high-capacitance gate dielectric layers as well as high-resolution printed silver electrodes, which provides promising bases for producing practical active-matrix OTFT backplanes.

Morphological control of energetic materials (EM) is highly desired because ill-defined morphology arising from variations in processing method and supplier make it impossible to reproducibly engineer their physicochemical properties. As the most powerful, non nuclear energetic material to date, 2,4,6,8,10,12-hexanitro -2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) has been the subject of significant interest for improved applications in military grade explosives. Here we report a new method for recrystallization of CL-20 from irregular bulk EMs using a surfactant assisted self-assembly process to produce uniform spherical micron-sized particles. Detailed electron microscopy studies indicate that surfactant plays a critical role in controlling CL-20 morphology. Combined X-ray diffraction and Raman spectroscopy results reveal that the resultant spherical CL-20 particles exhibit an orthorhombic β-phase crystal structure. This material is expected to display enhanced functional reproducibility due to its monodisperse nature as well as decreased shock sensitivity due to their sub-micron particle size.

High-power single-mode (SM) and multi-mode (MM) InGaAs-AlGaAs strained quantum well (QW) lasers with emission wavelengths of 910 − 980 nm are extensively used in various fiber lasers and amplifiers for both telecom and defense applications. In particular, underseas and satellite communication systems require stringent reliability from these lasers. Since these lasers predominantly fail by catastrophic and sudden degradation due to COD, it is crucial especially for space satellite applications to investigate reliability, failure modes, and degradation mechanisms of these lasers. Catastrophic optical mirror damage (COMD) was known to be the only failure mode until our group reported a new failure mode in MM and SM InGaAs-AlGaAs strained QW lasers in 2009 and 2016, respectively. Our group reported that bulk failure due to catastrophic optical bulk damage (COBD) has become the dominant failure mode of both SM and MM lasers. Since there have been limited reports on COBD compared to COMD, the intent of this paper is to introduce our studies on COBD that have spanned the last decade. We investigated reliability, failure modes, and degradation processes in SM and MM InGaAs-AlGaAs strained QW lasers by performing short-term step-stress tests and long-term accelerated life-tests as well as failure mode analyses using various nondestructive and destructive micro-analytical techniques including electron beam induced current (EBIC), time-resolved electroluminescence (EL), deep level transient spectroscopy (DLTS), focused ion beam (FIB), and high-resolution TEM. EBIC and EL techniques were employed to study dark line defects generated in degraded lasers stressed under different test conditions. Time-resolved EL techniques were employed to study initiation and progressions of dark spots and dark lines in real time as lasers were aged. DLTS techniques were employed to study electron traps in both pristine and degraded lasers. Lastly, FIB and high-resolution TEM were employed to prepare cross sectional and plan view TEM specimens to study DLD areas in post-aged lasers. We also report our current understanding on degradation mechanisms responsible for COBD in both SM and MM lasers.

In situ X-ray absorption near edge structure (XANES) measurements were conducted to elucidate the chemical states of Co and Ni catalysts during single-walled carbon nanotube (SWCNT) growth via chemical vapor deposition (CVD). XANES spectra indicated that both Co and Ni catalysts partially oxidized before heating. It was found that Co catalysts formed carbides during the SWCNT growth. In contrast, Ni catalysts remained metallic state even after the SWCNT growth had begun. These results indicate that during SWCNT growth, carbon atoms dissolve into Co particles, whereas for Ni particles, they diffuse on the surface region. It was concluded that the growth mechanisms of SWCNTs formed by CVD differed for either Co or Ni catalyst.

In this study, AlGaN/GaN high electron mobility transistors (HEMTs) with a two-dimensional hole gas (2DHG) were investigated. In addition to a two-dimensional electron gas (2DEG) formed at the interface of the AlGaN and GaN layers for being a channel, a 2DHG was designed and formed underneath the channel to be the back gate. The simulated results showed the operation of device can be depletion-mode and enhancement-mode by adjusting the back gate bias. The fabricated devices showed the feasibility of 2DHG back gate control.

Understanding the precipitation of brittle hydride phases is crucial in establishing a failure criterion for various zirconium alloy nuclear fuel cladding. Accordingly, it is important to quantify the sensitivity of hydride precipitation to the component microstructure. This experimental investigation focuses on two microstructural characteristics and their role as hydride nucleation sites: The grain size and the alloy chemical composition. Samples of commercially pure zirconium (Zr-702) and Zircaloy-4, each with a wide range of grain sizes, were hydrided to 100 ppm and micrographs of the hydride distribution were optically analyzed for inter-granular and intra-granular precipitate sites. For most grain sizes, it was found that a significantly lower fraction of the precipitated hydrides nucleated at grain boundaries in Zircaloy-4 than in Zr-702, suggesting that a higher SPP content encourages the formation of intra-granular hydrides. Moreover, this effect became more prominent as the grain size increased; large-grain specimens contained a higher fraction of intra-granular hydrides than small-grain specimens of both Zr-702 and Zircaloy-4, highlighting the potency of grain boundaries as nucleation sites and how SPPs can influence the hydride distribution profile.

Tumor tissue has different acidity compared to normal tissue. Localized drug delivery that release chemotherapeutic medications upon stimulation via pH changes is a promising strategy in cancer therapy for adjuvant therapies after surgical resection to reduce the risk of local recurrence. In this study, a mesoporous nanofibrous system with acidic pH-triggered “caps” has been for the first time developed for localized on-demand drug release to target tumor cells, without biological damage to normal cells while maintaining their structural integrity to support future tissue regeneration. Specifically, polyacrylic acid (PAA) was grafted on electrospun mesoporous silica nanofibers (MSFs) and the obtained PAA-MSFs allowed efficient drug loading at neural pH and on-demand releasing at acidic cancer subcellular compartments, based on pH-dependent electrostatic interactions associated with protonation/deprotonation of PAA. The The hybrid mesoporous nanofibers a low cytotoxicity to normal cells and a high killing efficiency to cancer cells. The system demonstrated a great potential as tumor targeting drug delivery system.

The Connecticut (CT) State Colleges and Universities’ College of Technology (COT) and its Regional Center for Next Generation Manufacturing (RCNGM), a National Science Foundation (NSF) Center of Excellence, educate manufacturing technicians with necessary skills as needed by the manufacturing industry. The COT-RCNGM continuously broadens its partnerships with other community colleges, high schools and industry in New England and at the national and international levels to provide support and expertise to both students and educators in advanced manufacturing programs. The COT was founded in 1995 through state legislation to create and implement seamless pathways in engineering and technology. This system-wide collaboration of all twelve CT public community colleges, including seven state-of-the-art Advanced Manufacturing Technology Centers (AMTC) at CT’s community colleges; eight public and private universities; technical high and comprehensive high schools; and representatives from industry, including the CT Business & Industry Association (CBIA) which represents 10,000 companies. The pathways have multiple points of entry and exit for job placement and stackable credentials for degree completion, including national certifications that have increased enrollments and created program stability.

The COT is led by the Site Coordinators Council that meets monthly and consists of faculty and deans from all COT educational partners and representatives from industry and government. The Council identifies and reviews new programs, concentrations, and certificates based on industry needs and creates seamless articulated pathways. Final approval is often completed within three months for immediate implementation, allowing a timely response to workforce needs. The COT-RCNGM partners with CBIA to conduct a biannual survey of manufacturing workforce needs in CT. Educators use the survey to identify curricular needs and support funding proposals for educational programs. Asnuntuck Community College, the original AMTC, was able to use industry data from the survey to help create new programs. The RCNGM partners with other NSF grants and entities such as the National Network for Manufacturing Innovation (NNMI). The COT-RCNGM produced DVDs profiling students who have completed COT programs and work in CT manufacturing companies. The Manufacture Your Future 2.0 and the You Belong: Women in Manufacturing DVDs are distributed nationally to increase knowledge of career opportunities in manufacturing. Finally, the COT-RCNGM organizes the Greater Hartford Mini Maker Faire that brings together community members of all ages and backgrounds to share projects that promote interest in STEM fields. Participation in the Maker Movement led to involvement in a national network of Maker Faire organizers including a meeting at the White House where one organizer from each state was invited to attend and discuss the national impact of Makers.