New Mechanism for the Reduction of Vanadyl Acetylacetonate to Vanadium Acetylacetonate for Room Temperature Flow Batteries.

In this study, a new mechanism for the reduction of vanadyl acetylacetonate, VO(acac) , to vanadium acetylacetonate, V(acac) , is introduced. V(acac) has been studied for use in redox flow batteries (RFBs) for some time; however, contamination by moisture leads to the formation of VO(acac) . In previous work, once this transformation occurs, it is no longer reversible because there is a requirement for extreme low potentials for the reduction to occur.

New insights into the electrode mechanism of lithium sulfur batteries via air-free post-test analysis.

Effects of the volume expansion and shrinkage of Li2S cathodes on electrochemical cycle life are investigated via post-test analysis without exposure to air. The engineered electrodes that confine volume changes within micro-reactors have significantly longer life than the electrodes without the micro-reactor structure, providing the first unambiguous evidence of the importance of confining volume changes for improved battery performance.

An Ambient Temperature Molten Sodium-Vanadium Battery with Aqueous Flowing Catholyte.

In this study, we have investigated the key factors dictating the cyclic performance of a new type of hybrid sodium-based flow batteries (HNFBs) that can operate at room temperature with high cell voltages (>3 V), multiple electron transfer redox reactions per active ion, and decoupled design of power and energy. HNFBs are composed of a molten Na-Cs alloy anode, flowing aqueous catholyte, and a Na-β″-Al2O3 solid electrolyte as the separator. The surface functionalization of graphite felt electrodes for the flowing aqueous catholyte has been studied for its effectiveness in enhancing V(2+)/V(3+), V(3+)/V(4+), and V(4+)/V(5+) redox couples.

Silicon as a potential anode material for Li-ion batteries: where size, geometry and structure matter.

Silicon has attracted huge attention in the last decade because it has a theoretical capacity ∼10 times that of graphite. However, the practical application of Si is hindered by three major challenges: large volume expansion during cycling (∼300%), low electrical conductivity, and instability of the SEI layer caused by repeated volume changes of the Si material. Significant research efforts have been devoted to addressing these challenges, and significant breakthroughs have been made particularly in the last two years (2014 and 2015).

PVP-Assisted Synthesis of Uniform Carbon Coated Li2S/CB for High-Performance Lithium-Sulfur Batteries.

The lithium-sulfur (Li-S) battery is a great alternative to the state-of-the-art lithium ion batteries due to its high energy density. However, low utilization of active materials, the insulating nature of sulfur or lithium sulfide (Li2S), and polysulfide dissolution in organic liquid electrolyte lead to low initial capacity and fast performance degradation. Herein, we propose a facile and viable approach to address these issues.

Bottom-up, hard template and scalable approaches toward designing nanostructured Li2S for high performance lithium sulfur batteries.

Li2S with a high theoretical capacity of 1166 mA h g(-1) and the capability to pair with lithium free anodes has drawn much attention for lithium sulfur (Li-S) battery applications. However, the fast battery decay and the low capacity retention due to dissolution of intermediate polysulfides in electrolytes limit its development. Designing a nanosized and nanostructured host for Li2S through facile techniques is one of the ways to alleviate the dissolution and improve Li-S battery performance; nevertheless, it is technically difficult to synthesize nanosized and nanostructured hosts for Li2S because Li2S is highly sensitive to moisture and oxygen.

Room Temperature, Hybrid Sodium-Based Flow Batteries with Multi-Electron Transfer Redox Reactions.

We introduce a new concept of hybrid Na-based flow batteries (HNFBs) with a molten Na alloy anode in conjunction with a flowing catholyte separated by a solid Na-ion exchange membrane for grid-scale energy storage. Such HNFBs can operate at ambient temperature, allow catholytes to have multiple electron transfer redox reactions per active ion, offer wide selection of catholyte chemistries with multiple active ions to couple with the highly negative Na alloy anode, and enable the use of both aqueous and non-aqueous catholytes. Further, the molten Na alloy anode permits the decoupled design of power and energy since a large volume of the molten Na alloy can be used with a limited ion-exchange membrane size.

Nanocrystalline hydroxyapatite with simultaneous enhancements in hardness and toughness.

Using a series of dense hydroxyapatite (HA) bodies with well controlled grain sizes ranging from sub-micrometers to nanometers, we show that simultaneous improvements in hardness and toughness can be attained for nanocrystalline (nc) HA. It is demonstrated that the hardness of HA follows the Hall-Petch relationship as the grain size decreases from sub-micrometers to nanometers. In the same grain size range, the toughness of HA increases by as much as 74% because of the enhanced crack deflection associated with a transition from transgranular to intergranular cracking, promoted by the reduced grain size in the nanoscale.

The long-term hydriding and dehydriding stability of the nanoscale LiNH2+LiH hydrogen storage system.

The long-term cyclic durability of nano-engineered solid-state hydrogen storage systems is investigated using LiNH2+LiH as a model system. Through 60 hydriding and dehydriding cycles over the course of more than 200 h, a small decrease in the kinetics of the dehydrogenation reaction leads to a 10% reduction in the amount of hydrogen liberated during a 2.5 h desorption.

Synthesis of high purity hydroxyapatite nanopowder via sol-gel combustion process.

A polymeric sol-gel combustion method has been used to synthesize nanocrystalline hydroxyapatite (HA) powder from calcium nitrate and triethyl phosphate with the addition of NH(4)OH. The sol-gel combustion process generates phase-pure nanocrystalline HA powder, as characterized using Fourier transform infrared (FTIR), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Sintering of the HA powder compact at 1200 degrees C for 2 h leads to a 93% theoretical dense ceramic body.

Enhancement of lithium amide to lithium imide transition via mechanical activation.

The decomposition of lithium amide (LiNH2) to lithium imide (Li2NH) and ammonia (NH3) with and without high-energy ball milling is investigated to lay a foundation for identifying methods to enhance the hydrogen uptake/release of the lithium amide and lithium hydride mixture. A wide range of analytical instruments are utilized to provide unambiguous evidence of the effect of mechanical activation. It is shown that ball milling reduces the onset temperature for the decomposition of LiNH2 from 120 degrees C to room temperature.

Stability of lithium hydride in argon and air.

The oxidation behaviors of LiH under a high purity argon atmosphere, an argon atmosphere with some O2 and H2O impurities, and ambient air at both room and high temperatures, are investigated using a variety of analytical instruments including X-ray diffractometry, thermogravimetry, mass spectrometry, scanning electron microscopy, and specific surface area analysis. The oxidation behaviors of the ball-milled LiH under different atmospheres are also studied and compared with those without ball milling. It is shown that no oxidation of LiH occurs under a high-purity argon atmosphere.

Microstructure of dental porcelains in a laser-assisted rapid prototyping process.

Objectives: The goals of this study were to investigate the phase transformation and microstructure of dental porcelain bodies densified via a moving laser beam and to develop an understanding of how the microstructure of the dental porcelain varies with the laser processing condition and the position relative to the center of the laser beam.

Methods: A moving laser beam was used to scan and densify a commercial dental porcelain powder bed. The porcelain powder compact was also sintered using a furnace at different temperatures.