The three-dimensional structure of crack tip dislocations in single crystal silicon was observed by combining high-voltage electron microscopy and tomography. It was revealed that dislocations cross-slipped proximal to the crack tip even in the initial stages of plastic deformation. The local stress intensity factor along the crack front was calculated by taking into account the experimentally determined dislocation character. Based on these observations and calculations, a model to account for the sequential multiplication of dislocation sources along the crack front is proposed.

Spinning carbon nanotube (CNT) thread directly from 4–6 mm long aligned carbon nanotube arrays is reported here. The strength of carbon nanotube thread was improved by optimizing the chemical vapor deposition parameters for growing long aligned carbon nanotube arrays. The morphological and structural characterization of CNT arrays and threads were studied by Raman spectroscopy, transmission electron microscopy, and scanning electron microscopy. After optimization of growth parameters threads were spun with diameters between 10 and 70 μm. We have achieved thread strength of about 280 MPa.

We have developed a new class of proton-conducting organic–inorganic hybrid silicophosphite membranes, produced by ethanol condensation of organically modified alkoxysilanes and anhydrous vinylphosphonic acid under solventless, catalyst-free, low-temperature, one-pot conditions. The membranes synthesized in this study are crack-free, large, and flexible, and they exhibit good thermal stability up to intermediate temperatures (~218 °C). Structural analyses using 29Si and 31P nuclear magnetic resonance spectroscopy and infrared measurements revealed that ethanol condensation produced an inorganic alternating copolymer structure, Si–O–P, with a phosphole group, and successive polymerization between vinyl and/or methacryl groups enabled these structures to connect with each other. In this way, it is possible to achieve structure manufacturing of inorganic–organic networks. The proton conductivities of the hybrids are as high as 5.2 × 10−3 S/cm at 85 °C under 80% relative humidity.

Polycrystalline BaTiO3 thin films have been prepared by hydrothermal reaction with sputter-deposited nanostructured reactive Ti templates designed to control net diffusion direction and distance. Templates were prepared in two morphologies, i.e., planar and nanopillar. The samples produced from flat templates showed sluggish transformation kinetics and an eventual termination of reaction without fully consuming the Ti metal. Templates with pillar morphology, on the other hand, could be transformed to phase-pure BaTiO3, independent of the template thickness. In the as-precipitated state, those films revealed a permittivity of ~1000 and loss tangent values around 0.1 with mild dispersion in the kilohertz frequency range. Annealing these films under forming gas containing 1 vol% H2 balance N2 for 3 h at 200 °C decreased high-field losses to 0.06 and reduced dispersion. Mn incorporation as an in situ acceptor dopant was also explored. Addition of Mn during hydrothermal treatment further improved the electrical properties. Annealing under the same postgrowth conditions virtually eliminated the frequency dispersion in the range of 1 kHz to 1 MHz, while maintaining permittivity values in the range of 350.

Mn-doped γ-Ga2O3 thin films with a defective spinel structure have been epitaxially grown on spinel (100) substrates using pulsed laser deposition. The crystal quality of the films is strongly dependent on preparation conditions, particularly substrate temperature and laser energy density, as well as Mn concentration. In the 7 cation% Mn-doped film grown under the optimized conditions, the full width at half maximum in the x-ray diffraction rocking curve for the (400) plane is 117 arcsec and the root-mean-square roughness of the surface is approximately 0.4 nm. These values are comparable to those of the spinel substrate. The film shows a uniform tetragonal distortion with a tetragonality of 1.05.

Weak-beam dark-field images of dislocations interacting with particles acquired over a large angular range were used to reconstruct tomograms, which were then used as the basis to construct a three-dimensional (3D) model of the dislocation structure. These capabilities facilitate viewing the dislocation structure from different directions, recovering the information lost in the electron beam direction. Coupling these capabilities and a method to include the specimen coordinate system within them with conventional dislocation analysis enables a full characterization of the dislocation microstructure in three dimensions. This approach is used to understand the 3D nature of the interaction of dislocations and a twist boundary with Al3Sc particles in an Al–Mg–Sc alloy.

Upon rapid heating to a high temperature (~800 °C), mixtures of nitrate compounds and urea created nano and submicron metal particles. The process (reductive/expansion synthesis, RES) results in atomic scale mixing. The product formed from mixed-nitrate (Fe + Ni) salts and urea created true metallic alloy. Unlike other product-from-powder synthesis processes, this process produced only zero valent metal. Initial work suggests this method is a scalable and efficient means for making metallic nanoparticles. Although this is primarily a phenomenological report, a preliminary model is presented: Initially, nitrates decompose to oxide; thus in the absence of urea metal oxide particles form, as in the case of combustion synthesis. In the case of urea/nitrate mixtures, there is a “convolution” of decomposition processes. Urea decomposes to yield reducing gases, leading to the formation of metal rather than oxide. Rapid “expansion” of gas leads to “shattering,” resulting in highly dispersed particles.

This work reports the continuous and large-scale production of multiwalled carbon nanotubes (MWCNTs) from xylene/ferrocene in a swirled floating catalyst chemical vapor deposition reactor using argon as the carrier gas. The concentration of ferrocene used was 0.01 g/mL of xylene. In every run, 50-mL xylene gas was used together with xylene/ferrocene mixture injected into the reactor by means of a burette. The MWCNTs produced were characterized using the transmission electron microscopy (TEM) and Raman spectra. TEM analysis showed a poor production rate at 850 °C and a good production in the range of 900–1000 °C with optimal production rate at 950 °C. Furthermore, xylene/ferrocene mixture produced more MWCNTs at 950 °C with H:Ar (1:7) as the carrier gas. The diameters of the MWCNTs in the temperatures studied ranged from 15 to 95 nm with wall thicknesses between 0.5 and 0.8 nm.

La2NiMnO6 (LNMO) was prepared by a combustion method followed by heating at high temperature. Subsequently, the preformed LNMO was annealed in air, oxygen, or N2 atmosphere and characterized by powder x-ray diffraction (XRD), neutron diffraction, superconducting quantum interference device magnetometry, and dielectric analysis. Structural studies by XRD and neutron diffraction revealed the coexistence of partially cation disordered monoclinic (31%) and rhombohedral (69%) phases in the sample annealed in air. However, the sample annealed in oxygen shows about 50:50% of monoclinic and rhombohedral phases. Relaxor-like behavior with relative permittivity of the order of 104 was observed in the sample annealed in air, while relative permittivity decreases to about 200 in samples annealed in oxygen atmosphere. The magnetic properties indicate a well-defined ferromagnetic phase in the oxygen-annealed sample compared to a feeble ferromagnetic signature in the air-annealed one. The dielectric and ferromagnetism of LNMO samples have been related to formation and annihilation of oxygen vacancies.