A group of traditional pottery workshops in Sichuan Province, China, produce a unique coal-clay composite ceramic that is fired using a similarly unique kiln design and two-stage firing procedure not seen in any other ceramic tradition. Here we report on field and laboratory efforts to better understand this unusual ceramic material and technology, the functional advantages as cookware, braziers, and large storage vessels that include high strength and high thermal shock resistance, and the cultural context that supported the creativity and experimentation needed to develop such an innovative technology.

TiAl based alloys are desirable materials for turbine blades in aircraft engines. Depending on alloy composition and temperature additionally disordered β-Ti(Al) (A2 structure) or ordered βo-TiAl (B2 structure) can occur. Unfortunately little is known about the exact order/disorder transformation temperatures of β/βo.

We used the good contrast of neutron diffraction for ordering and disordering of TiAl alloys to determine the order/disorder temperatures, which are not accessible by other methods like DSC measurements. Several binary TiAl alloys as well as alloys with additional alloying elements were used to investigate the influence of different Al concentrations and alloying additions on the occurring ordering/disordering reactions and phase transformations. As a result ordered βo phase was found only in selected ternary alloys.

Magnesium oxide aerogels were made by sol-gel process using magnesium methoxide as precursor, methanol and deionized water as solvent with ethanol supercritical fluid drying. The influences of the different factors on the gel time and the specific surface area of magnesium oxide aerogels were studied, and the structure and morphology were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscope (TEM) and X-ray diffraction (XRD), and the Small Angle X-ray Scatter (SAXS) was utilized to determine the fractural structure of the magnesium oxide aerogels. The results show that MgO aerogels belong to the typical mesoporous materials with rich network and highly developed pore structure, and the specific surface area is 904.9 m2/g, the apparent density is 0.055 g/cm3, the average pore size is 19.6 nm. The results of SAXS analysis show that the fractal dimension of the MgO aerogels is 2.32 in high q area which proves the existence of rough surface and pore fractal structure.

The radiation environment of space poses a challenge for electronic systems, in particular flash memory, which contains multiple radiation-sensitive parts. Resistive memory (RRAM) devices have the potential to replace flash memory, functioning as an inherently radiation resistant memory device. Several studies indicate significant radiation resistance in RRAM devices to a broad range of radiation types and doses. In this study, we focus on the effect of displacement damage on tantalum oxide-based RRAM devices, as this form of damage is likely a worst-case scenario. An Ar+ (170 keV) ion beam was used to minimize any contribution from ionization damage, maximizing the effect of displacement damage. Fluence levels were chosen to generate enough oxygen vacancies such that devices in the high resistance state (HRS) would likely switch to the low resistance state (LRS). More than half of devices tested at the highest fluence level (1.43E13 ions/cm2) switched from HRS to LRS. The devices were then switched for 50 set/reset cycles, after which the radiation-induced resistance shift disappeared. These results suggest that device switching may mitigate radiation damage by accelerating oxygen vacancy-interstitial recombination.

Intermetallic ternary nanoalloys (NA) have increasingly gained prominence as excellent catalysts. But, their size, morphology and chemical compositions affect their catalytic and interfacial activities significantly. In this study, we present laser-induced breakdown spectroscopy (LIBS) for rapid quantitative elemental composition characterization of ternary NAs with different elemental ratios. Specifically, we use a calibration-free approach with LIBS to estimate the elemental ratios of PtCuCo ternary NAs with various stoichiometric ratios synthesized via our in-house laser ablation synthesis in solution-galvanic replacement reactions (LASiS-GRR) technique. The size and morphology of the samples are determined from transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX) measurements. The LIBS quantitative estimations for the NA samples are compared with results from inductively coupled plasma-optical emission spectroscopy (ICP-OES). The elemental ratio results of quantitative LIBS show good agreement with ICP-OES results, while being devoid of any external standard requirements or extensive sample preparations.

This work aims to develop magnetic fibers whose magnetic properties improve upon fibers produced using existing techniques. The goal of this work is to develop magnetic fibers that are magnetically anisotropic, with high squareness ratios when the fibers are oriented parallel to the applied magnetic field, and lower square ratios when the fibers are oriented perpendicular to the field. In this work, barium hexaferrite particles were embedded in a Sylgard elastomer matrix. The magnetic material was placed on a sheet of acrylic with spacers on opposite ends. A top sheet of acrylic was placed on the spacers. A 0.5 T permanent magnet was placed on top of the upper piece of acrylic. Magnetic fibers were drawn as the material aligned itself with the magnetic field lines of the magnet. After the fibers cured they were tested on a vibrating sample magnetometer at angles parallel and perpendicular to the field. The results showed that the fibers were highly anisotropic, with an average squareness ratio of 0.82 in the easy axis and an average squareness ratio of 0.34 in the hard axis. Although, the fibers were anisotropic, there was a high variability in the magnetization when normalized by the total volume of the fiber. This indicates that the magnetic content varies within each fiber, likely due to the variation in the strength of the magnetic field lines of the external magnet. This research demonstrated that magnetic fibers with high anisotropy can be fabricated, but the amount of magnetic material in each fiber from the same batch needs to be tuned to decrease variability. Fitting this experimentally found squareness ratio to a von Mises distribution, the concentration parameter was calculated to be 0.14. This indicates the magnetic domains within each fiber are highly aligned with the externally applied field.

Two sets of rectangle samples with different length/width ratios were prepared and subjected to uniaxial compression in the normal direction of rolled pure titanium. Results from Electron backscatter diffraction (EBSD) show that the produced {11 $\bar 2$ 2} twins in the two sets of samples exhibit different orientations, which is related to the variant selection of twinning behaviors with respect to the length/width ratios of the samples. The variant selection criterion is investigated in terms of the Schmid factors and contribution of the active twins to external strain, which indicates that the variants resulting in the elongation along the longer direction of the sample were unfavorable.

Copper-based pigments are common in works of art that show signs of decay on green and blue areas and are frequently associated with the degradation of organic substrates and/or media (drying oils, cellulose, etc.). The exact causes of degradation remain unknown. This prompted us to study possible starting and degradation products of one especially reactive copper pigment, verdigris (copper acetate), as well as pigments of the same family (salt and soap greens). Preparation of pigments using historical methods was followed by spectroscopic and crystallographic characterization using Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Synthesis of verdigris and verdigris-like pigments resulted in a mixture of starting polymorphs of verdigris, including neutral and basic verdigris. With accelerated aging, pigments degraded to a polymorph of basic verdigris when not affected by organic media, whereas pigments on cellulosic substrates showed oxidized copper species. With this study, we are beginning to understand verdigris starting materials and highlight the complex interactions between pigments and substrates that influence pigment degradation pathways.

The use of modern graphenic materials for improving oxygen barriers in food packaging and anti-corrosion barriers in coatings is explored by compounding and casting graphene nanoplatelets (GNP) with polyethylene (PE) and epoxy (EP). The GNP / PE films show comparable oxygen transmission rates to the neat PE films, indicating that further processing will be necessary to realize the desired enhancements. Early corrosion tests indicate that the GNP / EP coatings are providing more protection than the neat EP coatings on steel. Experiments to expand on these results are underway.

In this work, we describe the combination of hydrothermal and atomic layer deposition (ALD) for growing low-resistivity ZnO polycrystalline continuous films. The effect of the thickness of ALD seed layers on the morphology of the hydrothermal ZnO films was studied. It was shown that ZnO films hydrothermally deposited on very thin seed layer consist of separate nanorods but in the case of 20 nm seed layer ZnO films transform to uniform continuous layers comprising of closely packed vertically aligned crystallites. Photoluminescence spectra were shown to exhibit broad band behavior in the visible range, corresponding to radiative recombination processes via oxygen defects of ZnO crystalline lattice, and narrow band in the UV region, associated with band-to-band recombination processes. It was shown that the resistivity of the obtained ZnO films is decreased gradually with the increase of ZnO films thickness and determined by the presence of crystal lattice defects in the seed layer.

Research of electrostrictive polymers has generated new opportunities for harvesting energy from the surrounding environment and converting it into usable electrical energy. Electroactive polymer (EAP) research is one of the new opportunities for harvesting energy from the natural environment and converting it into usable electrical energy. Piezoelectric ceramic based energy harvesting devices tend to be unsuitable for low-frequency mechanical excitations such as human movement. Organic polymers are typically softer and more flexible therefore translated electrical energy output is considerably higher under the same mechanical force. In addition, cantilever geometry is one of the most used structures in piezoelectric energy harvesters, especially for mechanical energy harvesting from vibrations. In order to further lower the resonance frequency of the cantilever microstructure, a proof mass can be attached to the free end of the cantilever. Mechanical analysis of an experimental bimorph structure was provided and led to key design rules for post-processing steps to control the performance of the energy harvester. In this work, methods of materials processing and the mechanical to electrical conversion of vibrational energy into usable energy were investigated. Materials such as polyvinyledenedifluoridetetra-fluoroethylene P(VDF-TrFE) copolymer films (1um thick or less) were evaluated and presented a large relative permittivity and greater piezoelectric β-phase without stretching. Further investigations will be used to identify suitable micro-electromechanical systems (MEMs) structures given specific types of low-frequency mechanical excitations (10-100Hz).

Many computational and experimental analyses of molecular excitation rely on relative atomic velocities to identify the excitation of chemical bonds. These are often interpreted through the aid of normal mode calculations. We address two potential gaps in this approach: 1. Relative velocities may not reflect the total potential energy absorbed by the bond. 2. Normal mode calculations omit interactions between neighboring molecules, effectively assuming a similarity between condensed- and gas-phase chemistry. Phonon calculations implicitly include interactions between neighboring molecules and allow analyses of both relative velocities and potential energies in solids.In the present work, we compare kinetic and potential energy fractions of the phonon modes of the molecular solids nitromethane and β-HMX. We show that velocity-based methods are likely sufficient to analyze nitromethane. However, they cannot detect the majority of excitation ofthe N-N bonds in β-HMX, the scission of which appears to begin major decomposition pathways in the molecules.In the broader context of condensed-phase chemistry, this implies that important interactions may not all be identifiable through analyses that rely solely on relative atomic velocities.

To promote the energy density of lithium-ion battery, the sulfur-based cathode has attracted extensive attention because of its high specific capacity of 1672 mAh g-1 and its high abundance. However, the sulfur shuttling effects and the loss of active material during lithiation hinder its commercial application. To tackle these issues, we synthesized a stable copolymer-sulfur composite by chemically binding sulfur. The composite with 86% sulfur content was prepared using 1,3-diethynylbenzen and sulfur particles via scalable invers vulcanization. The sulfur content in copolymer sulfur was achieved as high as 86%. Our copolymer-sulfur composite cathode showed excellent cycling performance with a specific capacity of 454 mAh g-1 at 0.1 C after 300 cycles. We demonstrate that the organosulfur-DEB units in the copolymer-sulfur composite serve as the ‘plasticizer’ to effectively prevent the polysulfide shuttling.

We report the synthesis of MoS2(1-x)Te2x by co-sputtering deposition and effect of mixture on its bandgap. The deposition was carried out at room temperature, and the sputtering power on individual MoS2 and MoTe2 targets were varied to obtain films with different compositions. Investigation with X-ray photoelectron spectroscopy confirmed the formation of Mo-Te and Mo-S bonds after post-deposition annealing (PDA), and one of the samples exhibited composition ratio of Mo:S:Te = 1:1.2:0.8 and 1:1.9:0.1 achieving 1:2 ratio of metal to chalcogen. Bandgap of MoS1.2Te0.8 and MoS1.9Te0.1 was evaluated with Tauc plot analysis from the extinction coefficient obtained by spectroscopic ellipsometry measurements. The obtained bandgaps were 1.0 eV and 1.3 eV. The resulting bandgap was lower than that of bulk MoS2 and higher than that of bulk MoTe2 suggesting mixture of both materials was achieved by co-sputtering.

We report on the structural and electrical properties of epitaxial SmN thin films grown by molecular beam epitaxy. The effect of the growth temperature and nitrogen precursor, either pure molecular N2 or NH3 was investigated. The structural quality of SmN was assessed by X-ray diffraction and the epitaxial growth character is observed over the entire range of growth temperatures, from 300°C to 800°C, with both nitrogen precursors. The highest quality films are produced at a growth temperature of about 430°C by using N2 as a nitrogen precursor. Hall Effect and resistivity measurements establish that SmN films are heavily n-type doped semiconductors, suggesting the presence of nitrogen vacancies, a recurring phenomenon in rare earth nitride compounds.

We demonstrate theoretically the possibility for the Bose-Einstein condensation of excitons in properly selected double walled carbon nanotube structures. The condensation mechanism is enabled by the interaction of excitons residing on one tubule with the near-field generated by the plasmon mode of the other coaxial tubule, resulting in new hybridized bosonic quasiparticles called exciton-plasmons. We derive the dispersion relation for the exciton-plasmons, and calculate the exciton participation rate in the exciton-plasmon condensate. The requirements for forming the appropriate double walled carbon nanotube combinations capable of the optimum exciton-plasmon coupling regime needed to realize the condensation effect, as well as the possibility of experimental observation of the phenomenon, are discussed.

The objective of this research work is to study the weldability of a Nb microalloyed TWIP steel through welding nuggets generated by Gas Tungsten Arc Welding process. Weldability was examined by microstructural changes in the fusion zone (FZ) and heat affected zone (HAZ) using light optical metallography (LOM), segregation in the nuggets was evaluated using elemental mappings of chemical analysis by Scanning Electron Microscopy and Electron Dispersive Spectroscopy (SEM-EDS), phase transformations were evaluated using X-ray diffraction (XRD) and the hardness properties were examined using Vickers microhardness testing (HV25). Experimental results show that microstructure of welding nuggets consists of austenitic dendritic grains in the FZ and equiaxed grains in the HAZ. FZ width and HAZ grain growth tend to increase as the heat input increases. Additionally, the studied Nb-containing TWIP steel showed segregation in the FZ, where Mn and Si segregated in the interdendritic regions, while Al and C preferentially segregated in dendritic areas. In general, the data obtained by XRD indicated that GTAW process did not affect austenite stability. Finally, the welding nuggets of studied TWIP steel showed lower microhardness values than the as-solution condition (starting condition). However, the heat affected zone showed hardened areas, which are associated with NbC precipitation hardening.

Hydrogels have been widely used in many applications from tissue engineering to drug delivery systems. For both tissue engineering and drug delivery, the mechanical properties are important because they would affect cell-materials interactions and injectability of drugs encapsulated in hydrogel carriers. Therefore, it is important to study the mechanical properties of these hydrogels, particularly at physiological temperature (37°C). This study adopted strain sweep and frequency sweep rotational rheological tests to investigate the rheological characteristics of various tissue engineering relevant hydrogels with different concentrations at 37°C. These hydrogels include alginate, RGD-alginate, and copolymerized collagen/alginate/fibrin. It has revealed that the addition of RGD has negligible effect on the elastic modulus and viscosity of alginate. Alginate gels have demonstrated shear thinning behavior which indicates that they are suitable candidates as carriers for cells or drug delivery. The addition of collagen and fibrin would reinforce the mechanical properties of alginate which makes it a strong scaffold material.

The carbon dots were investigated to reveal their light-emitting mechanism. The fluorescence spectra of carbon dots show typically two different types of photoluminescence: the excitation-independent component in the short wavelength, and the excitation-dependent component in the longer wavelength. The UV-Vis spectrum of carbon dots shows the absorption maximum of 340 nm which should be accredited to the n-π* transition of the carbonyl group in carbon dots. Absolute quantum yields of carbon dots dispersed in Polyvinyl alcohol is around 15% when the excitation wavelength is less than 425 nm, but decreases continuously when the excitation wavelength increases. The decay lifetimes of the carbon dots also show an abrupt change at excitation wavelength 425 nm. Time resolved photoluminescence was implemented from 31K to 291K to study the photoluminescence decay dynamics of carbon dots, resulting in the continuously decreasing of the lifetime as the temperature increases.

We have found that several nitrogen-related luminescence centers appear at 389 nm, 503 nm (H3 center), 575 nm (NV0 center), 637 nm (NV- center) in single-crystalline Ib diamond cut by means of a YAG laser irradiation process, followed by a suitable hydrogen microwave-plasma treatment, and that cathodoluminescence peaks related to these centers substantially change in intensity by irradiating the sample with 15-keV electron beam (EB). The relative number of 389-nm centers originating from a pair of a substitutional nitrogen atom and an adjacent interstitial carbon atom increased while the concentrations of the vacancy-related centers were reduced with increasing 15-keV EB doses. These facts indicate that both the process-induced self-interstitials and the vacancies in the diamond rather easily moved to more preferential positions to form their stabler defect states, being suggestive of possibility to control densities of NV and NV-related centers.