Lithium sulfur (Li–S) batteries have the potential to provide higher energy storage density at lower cost than conventional lithium ion batteries. A key challenge for Li–S batteries is the loss of sulfur to the electrolyte during cycling. This loss can be mitigated by sequestering the sulfur in nanostructured carbon–sulfur composites. The nanoscale characterization of the sulfur distribution within these complex nanostructured electrodes is normally performed by electron microscopy, but sulfur sublimates and redistributes in the high-vacuum conditions of conventional electron microscopes. The resulting sublimation artifacts render characterization of sulfur in conventional electron microscopes problematic and unreliable. Here, we demonstrate two techniques, cryogenic transmission electron microscopy (cryo-TEM) and scanning electron microscopy in air (airSEM), that enable the reliable characterization of sulfur across multiple length scales by suppressing sulfur sublimation. We use cryo-TEM and airSEM to examine carbon–sulfur composites synthesized for use as Li–S battery cathodes, noting several cases where the commonly employed sulfur melt infusion method is highly inefficient at infiltrating sulfur into porous carbon hosts.

Over the past three decades, the combination of inorganic-nanoparticles and organic-polymers has led to a wide variety of advanced materials, including polymer nanocomposites (PNCs). Recently, synthetic innovations for attaching polymers to nanoparticles to create “hairy nanoparticles” (HNPs) has expanded opportunities in this field. In addition to nanoparticle compatibilization for traditional particle–matrix blending, neat-HNPs afford one-component hybrids, both in composition and properties, which avoids issues of mixing that plague traditional PNCs. Continuous improvements in purity, scalability, and theoretical foundations of structure–performance relationships are critical to achieving design control of neat-HNPs necessary for future applications, ranging from optical, energy, and sensor devices to lubricants, green-bodies, and structures.

Nanohybrid artificial membranes made by intercalation of amphiphilic molecules into the galleries of a layered host, exhibit characteristics similar to biological membranes and they can be used as sensors. Different responses have been observed even for molecules that have similar features for example, saccharin and its sodium salt suggesting that the nanohybrid might be useful in developing an electronic nose. The dynamic range of the saccharin sensor is 20 - 300μM. In this paper we present our results on sensor fabrication and testing and discuss possible sensing mechanisms. In addition, we describe our work on immobilizing in the nanohybrid membranes Glucose Oxidase, Horseradish Peroxidase and Gramicidin and evaluating their performance.

Polycrystalline GaN layers have been produced on generic substrates via spin coating. Based on X-ray diffraction and SEM analyses, the GaN particles appear to be highly oriented on the surface. Strong luminescence from these layers has been demonstrated by cathodoluminescence. The source material was high purity, high quality GaN powder produced in our laboratory. Methyl cellulose was successfully used to disaggregate GaN particles in the dispersion. The colloidal dispersions were spun onto different substrates: Si, sapphire and glass. The dispersant was removed by annealing the sample at 500°C. The layer thickness was controlled by varying the number of spin coatings. Applications for spindeposited GaN layers include the fields of light emitting devices and random lasers.

Nanocomposites of α-hydroxy polyester, polylactide (PLA) and β-hydroxy polyester, polyhydroxybutyrate (PHB) with layered silicates have been successfully prepared by melt extrusion of PLA and PHB with organically modified montmorillonite (MMT) and fluoromica. The mechanical properties of the nanocomposites are improved compared to the neat polymers. Storage modulus increase up to 40% compared with the pure polymers by adding only 2–3 wt% nanoclay. Biodegradation can be controlled by the choice of the nanoclay used.

Reinforcement of polymers with a second phase, whether inorganic or organic, to produce a polymer composite is common in the production of modern plastics. Polymer nanocomposites (PNCs) represent a radical alternative to these conventional polymer composites.

Molecular Dynamics simulations have been used to investigate the rheological properties and dynamics of nanoscopically confined lubricating films. Comparative experimental studies of 10 to 20Å thin polymer films confined between mica-type layers explore the dynamics of similar systems, and confirm the computer simulation predictions. The use of model systems of polymers intercalated in layered mica-type silicates facilitates the study of SFA-like geometries with a variety of common analytical techniques, thus dramatically expanding the horizons of studying nanometer wide confined polymer films.

Polyetherimide-layered silicates nanocomposites with increased char yield and fire retardancy are described. The use of nanocomposites is a new, environmentally-benign approach to improve fire resistance of polymers.

Conventional three point bending and TEM techniques are employed to determine the fracture toughness and identify the failure mechanisms in model layered-silicate polymer nanocomposites.

Tantalum nitride thin films were produced by nitridation of sol-gel tantala thin films. The oxidation kinetics and the activation energy for oxidation were investigated and compared to those of sputtered tantalum nitride thin films. Data was gathered from in situ sheet resistance measurements taken between 550 and 720 K. Sol-gel films exhibited parabolic oxidation kinetics and had an activation energy of 1.9 eV. Sputtered films displayed quartic oxidation kinetics at lower temperatures tending toward cubic kinetics at higher temperatures and had an activation energy of 1.6 eV.

Ba0.75Sr0.25TiO3 thin films have been deposited on single-crystal MgO substrates by pulsed laser deposition with the objective of forming ferroelectric films with a low Curie temperature. The films have been characterized by capacitance measurements and by transmission electron microscopy, x-ray diffraction, and Rutherford backscattering spectrometry (random and channeled). Films deposited with the substrate at 500 °C are polycrystalline, while those deposited at 650 °C are highly aligned and possibly epitaxial. The films are transparent in the visible region with an optical absorption edge at about 300 nm. Capacitance measurements on the polycrystalline films reveal a Curie transition at 283 K. The lowering of Curie temperature from the corresponding bulk sample is attributed to the films being under compression, as verified by Raman spectroscopy.

We have investigated the tribomechanical properties of ion-beam-densified sol-gel zirconia overlayers on bulk zirconia. Ion irradiation of the sol-gel films leads to hydrogen, oxygen, and carbon losses as indicated by Rutherford backscattering spectrometry and forward recoil energy spectroscopy. Ellipsometry measurements show that the film thickness decreases with increasing dose. The microhardness exhibits an increase and subsequent decrease with dose. Friction measurements along with profilometry measurements indicate that severe abrasive wear of the film takes place in the first 1000 cycles after which point the substrate is in direct contact with the pin.

We have investigated the densification behavior of sol-gel zirconia films resulting from ion irradiation. Three sets of films were implanted with neon, krypton, or xenon. The ion energies were chosen to yield approximately constant energy loss through the film and the doses were chosen to yield similar nuclear energy deposition. Ion irradiation of the sol-gel films resulted in carbon and hydrogen loss as indicated by Rutherford backscattering spectrometry and forward recoil energy spectroscopy. Although the densification was hypothesized to result from target atom displacement, the observed densification exhibits a stronger dependence on electronic energy deposition.

Nanometer size lead iodide particles have been synthesized in the porous network of a cross-linked polymer matrix. The optical band gap of the nanocrystals is shifted towards higher energy as compared to the bulk value. This shift is attributed to the quantum size effect on excitons. Intercalation with aniline leads to a further shift in the band gap which depends on the dipole moment of the intercalated guest species. Differential scanning calorimetry and high temperature x-ray diffraction have been used to analyze the ferroelectric transition in Pbl2.

Artificial membranes possessing physicochemical properties similar to biological membranes have been synthesized by immobilization of synthetic amphiphiles in layered ceramics. The intercalated bilayer-forming amphiphiles exhibit a gallery height of about 39 Å. Retention of bilayer-forming characteristics is further confirmed by the presence of a crystal to liquid-crystal phase transition. A dramatic increase in the membrane capacitance at the tansition temperature is attributed to an increase in membrane fluidity.

Nanometer-scale iron oxide magnetic particles have been formed in the porous network of a cross-linked polymer matrix by ion exchange and subsequent hydrolysis. The oxide particles are uniform, well-dispersed and spherical with a diameter ranging between 30 and 1200 Å depending on the synthesis conditions. The DC magnetic susceptibility, measured between 4 and 300 K, continuously increases with decreasing temperature and tends to saturate at low temperatures. Composites containing iron oxide particles with an average diameter of 80 Å exhibit superparamagnetism while those on the order of 1000 Å undergo an antiferromagnetic-type transition at 33 K. The magnetic susceptibility is critically dependent upon the particle size and the strength of the magnetic field.