Fluorine in Complex Alumino-Boro-Silicate Glasses: Insight into Chemical Environment and Structure.

Fluorine incorporation into silicate glasses is important for technical fields as diverse as geophysics, extractive metallurgy, reconstructive dentistry, optical devices, and radioactive waste management. In this study, we explored the structural role of fluorine in alkaline alumino-borosilicate glass, with increasing amounts of fluorine up to 25 mol % F while maintaining the glass composition. Glasses were characterized by X-ray diffraction (XRD), Al and F magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, and electron probe microanalysis.

Toward High-Performance Metal-Organic-Framework-Based Quasi-Solid-State Electrolytes: Tunable Structures and Electrochemical Properties.

Metal-organic frameworks (MOFs) have been reported as promising materials for electrochemical applications owing to their tunable porous structures and ion-sieving capability. However, it remains challenging to rationally design MOF-based electrolytes for high-energy lithium batteries. In this work, by combining advanced characterization and modeling tools, a series of nanocrystalline MOFs is designed, and the effects of pore apertures and open metal sites on ion-transport properties and electrochemical stability of MOF quasi-solid-state electrolytes are systematically studied.

Temperature-Dependent Anisotropic Refractive Index in β-GaO: Application in Interferometric Thermometers.

An accurate knowledge of the optical properties of β-GaO is key to developing the full potential of this oxide for photonics applications. In particular, the dependence of these properties on temperature is still being studied. Optical micro- and nanocavities are promising for a wide range of applications.

A Bioinspired Coating for Stabilizing Li Metal Batteries.

With plenty of charges and rich functional groups, bovine serum albumin (BSA) protein provides effective transport for multiple metallic ions inside blood vessels. Inspired by the unique ionic transport function, we develop a BSA protein coating to stabilize Li anode, regulate Li transport, and resolve the Li dendrite growth for Li metal batteries (LMBs). The experimental and simulation studies demonstrate that the coating has strong interactions with Li metal, increases the wetting with electrolyte, reduces the electrolyte/Li side reactions, and significantly suppresses the Li dendrite formation.

Effect of extended defects on photoluminescence of gallium oxide and aluminum gallium oxide epitaxial films.

In this work, a systematic photoluminescence (PL) study on three series of gallium oxide/aluminum gallium oxide films and bulk single crystals is performed including comparing doping, epitaxial substrates, and aluminum concentration. It is observed that blue/green emission intensity strongly correlates with extended structural defects rather than the point defects frequently assumed. Bulk crystals or Si-doped films homoepitaxially grown on (010) β-GaO yield an intense dominant UV emission, while samples with extended structural defects, such as gallium oxide films grown on either (-201) β-GaO or sapphire, as well as thick aluminum gallium oxide films grown on either (010) β-GaO or sapphire, all show a very broad PL spectrum with intense dominant blue/green emission.

Reproduction of melting behavior for vitrified hillforts based on amphibolite, granite, and basalt lithologies.

European Bronze and Iron Age vitrified hillforts have been known since the 1700s, but archaeological interpretations regarding their function and use are still debated. We carried out a series of experiments to constrain conditions that led to the vitrification of the inner wall rocks in the hillfort at Broborg, Sweden. Potential source rocks were collected locally and heat treated in the laboratory, varying maximum temperature, cooling rate, and starting particle size.

Properties of Pertechnic Acid.

Dilute aqueous pertechnic acid has long been known as strong monoprotic acid that behaves as a simple pertechnetate ion in aqueous solution. As pertechnic acid concentrates by evaporation, it becomes yellow and then dark red, and dark-red crystalline material may ultimately be obtained. We show that as pertechnic acid concentrates, at least three compounds are formed: a yellow viscous liquid, a colorless (not red) crystalline solid, and a small amount of an intensely colored red-purple compound.

Structure and properties of NaFeSiO crystallized from 5NaO-FeO-8SiO glass.

The phase NaFeSiO [pentasodium iron(III) silicate] crystallizes readily from the NaO-FeO-SiO glass system in a relatively large compositional range. However, its crystal structure and properties have not been studied in detail since its discovery in 1930. In this work, the NaFeSiO phase was crystallized from a host glass with 5NaO·FeO·8SiO stoichiometry, and both the glass and the crystal were studied.

Compositional Dependence of Solubility/Retention of Molybdenum Oxides in Aluminoborosilicate-Based Model Nuclear Waste Glasses.

Molybdenum oxides are an integral component of the high-level waste streams being generated from the nuclear reactors in several countries. Although borosilicate glass has been chosen as the baseline waste form by most of the countries to immobilize these waste streams, molybdate oxyanions (MoO) exhibit very low solubility (∼1 mol %) in these glass matrices. In the past three to four decades, several studies describing the compositional and structural dependence of molybdate anions in borosilicate and aluminoborosilicate glasses have been reported in the literature, providing a basis for our understanding of fundamental science that governs the solubility and retention of these species in the nuclear waste glasses.

Pre-viking Swedish hillfort glass: A prospective long-term alteration analogue for vitrified nuclear waste.

Models for long-term glass alteration are required to satisfy performance predictions of vitrified nuclear waste in various disposal scenarios. Durability parameters are usually extracted from short-term laboratory tests, and sometimes checked with long-term natural experiments on glasses, termed analogues. In this paper, a unique potential ancient glass analogue from Sweden is discussed.

Chemical Trends in Solid Alkali Pertechnetates.

Insight into the solid-state chemistry of pure technetium-99 (Tc) oxides is required in the development of a robust immobilization and disposal system for nuclear waste stemming from the radiopharmaceutical industry, from the production of nuclear weapons, and from spent nuclear fuel. However, because of its radiotoxicity and the subsequent requirement of special facilities and handling procedures for research, only a few studies have been completed, many of which are over 20 years old. In this study, we report the synthesis of pure alkali pertechnetates (sodium, potassium, rubidium, and cesium) and analysis of these compounds by Raman spectroscopy, X-ray absorption spectroscopy (XANES and EXAFS), solid-state nuclear magnetic resonance (static and magic angle spinning), and neutron diffraction.

Regenerative feedback resonant circuit to detect transient changes in electromagnetic properties of semi-insulating materials.

A prototype regenerative feedback resonant circuit has been developed for measuring the transient spectral response due to perturbations in properties of various electromagnetic materials. The circuit can accommodate a variety of cavity resonators, shown here in the 8 GHz range, with passive quality factors (Qstat) as high as 7000 depending upon material loading. The positive feedback enhanced dynamic quality factors (Qdyn) of resonator∕material combinations in the regenerative circuit are on the order of 10(7)-10(8).

Combined charge carrier transport and photoelectrochemical characterization of BiVO4 single crystals: intrinsic behavior of a complex metal oxide.

Bismuth vanadate (BiVO4) is a promising photoelectrode material for the oxidation of water, but fundamental studies of this material are lacking. To address this, we report electrical and photoelectrochemical (PEC) properties of BiVO4 single crystals (undoped, 0.6% Mo, and 0.

Magnetic properties of double perovskite La2BMnO6 (B = Ni or Co) nanoparticles.

Double perovskite La2BMnO6 (B = Ni and Co) nanoparticles with average particle size of ~50 nm were synthesized using a facile, environmentally friendly, and scalable molten-salt reaction at 700 °C in air. Their structural and morphological properties were characterized by X-ray diffraction and transmission electron microscopy. Their magnetic properties were evaluated and compared using dc magnetic M-T and M-H, and ac magnetic susceptibility versus frequency, temperature, and field for the first time.

Rhenium solubility in borosilicate nuclear waste glass: implications for the processing and immobilization of technetium-99.

The immobilization of technetium-99 ((99)Tc) in a suitable host matrix has proven to be a challenging task for researchers in the nuclear waste community around the world. In this context, the present work reports on the solubility and retention of rhenium, a nonradioactive surrogate for (99)Tc, in a sodium borosilicate glass. Glasses containing target Re concentrations from 0 to 10,000 ppm [by mass, added as KReO(4) (Re(7+))] were synthesized in vacuum-sealed quartz ampules to minimize the loss of Re from volatilization during melting at 1000 °C.

Millimeter-wave dielectric properties of single-crystal ferroelectric and dielectric materials.

Transmittance measurements on various single crystal ferroelectric and dielectric materials, BaTiO(3), SrTiO(3), LiNbO(3), LiTaO(3), (PbMg(1/3)Nb(2/3)O(3))0.73-(PbTiO(3))0.27, LaAlO(3), and Bi(4)Ge(3)O(12), over a broad millimeter-wave (MMW) frequency range have been performed.

Magnetotransport properties of high quality Co:ZnO and Mn:ZnO single crystal pulsed laser deposition films: pitfalls associated with magnetotransport on high resistivity materials.

The electrical resistivity values for a series of pure and doped (Co, Mn, Al) ZnO epitaxial films grown by pulsed laser deposition were measured with equipment designed for determining the direct current resistivity of high resistance samples. Room-temperature resistances ranging from 7 x 10(1) to 4 x 10(8) Omega/sq were measured on vacuum-reduced cobalt-doped ZnO, (Al,Co) co-doped ZnO, pure cobalt-doped ZnO, Mn-doped ZnO, and undoped ZnO. Using a four-point collinear geometry with gold spring-loaded contacts, resistivities were measured from 295 to 5 K for resistances of < approximately 10(12) Omega/sq.