This study describes results from mechanical tests conducted on magnesium single crystals in comparison with polycrystalline magnesium. It was found by impact testing that the magnesium single crystal is highly ductile due to energy absorption by twinning and slip, while the polycrystalline samples fracture easily upon impact. Compressive testing along two orthogonal directions at low plastic strains was also performed. The microstructure studies by electron backscatter diffraction and XRD pole figure analysis revealed profuse ( $10\overline12$ ) twinning when compression is done along the growth plane (72 16 $\overline {88}$ 62). The twinning and interaction between different twin modes resulted in incipient recrystallization at strains as low as 8% at room temperature. Compression along the nearly orthogonal plane (2 2 $\bar{4}$ 15) was marked by a much lower degree of both twinning and recrystallization. The variation in microstructural response with the orientation of loading allows for a wide range for tailoring mechanical properties of pure magnesium single crystals without any need of alloying.

As the need for smaller data storage devices in the market continues to grow, the study of new combinations of self-assembled magnetic nanoparticles/films is greatly needed. In this research, Fe50-Ni50 films were synthesized using a Pulsed Laser Deposition technique. The films were analyzed using scanning electron microscopy (SEM), atomic force microscopy (AFM) and physical properties measurement system (PPMS). Films were deposited from Fe-Ni alloy target (50%-50% composition), deposition was conducted in vacuum, at substrate temperatures varying from liquid nitrogen temperature -196°C to 600°C. The films were annealed in a vacuum chamber at 600°C for 1 hour. The study reveals that the substrate temperature has significant effect on the structure of the films and their magnetic properties. It was shown that additional thermal treatment improved the quality of films in terms of narrow grain size distribution. Magnetic properties were also found to improve significantly after post annealing process.

Individual nanotubes made of carbon, boron nitride, iron, silicon, or other materials have properties such as high strength, toughness, electrical and thermal conductivity, and light weight that cannot be matched by conventional materials. Nanotubes also change their properties in response to external fields and change one type of energy into another, which are useful for design. This article explores three main steps in exploiting responsive materials based on nanotubes: nanotube synthesis, macroscale material fabrication, and incorporation into device structures for novel applications. Nanotubes are always synthesized as individual particles in the form of powders, smoke particles, or aligned forests. To be industrially important, nanotubes generally must be processed to form derivative materials such as functionalized/coated powders and forests and macroscale intermediate materials such as sheets, ribbon, and yarn. The processed nanotubes are then used to develop responsive materials and devices that are able to resist, react to, or generate energy from their environment. This article provides background information and ideas on how to develop nanotube responsive materials for everyday use.

Scandia-doped zirconia is a very promising material for solid oxide fuel cells due to its high oxygen conductivity in the 700-850°C temperature range. 10 mol% Sc2O3 - 1 mol% CeO2 - ZrO2 ceramics were sintered at temperatures 1100-1600°C using different heating rates and dwell times. Ceramics sintered at temperatures higher 1300°C were found to exist in cubic phase at room temperature and exhibit slow phase transformation from cubic (c) to rhombohedral (beta) phase between 330 and 400°C. Analysis of c-β phase transition efficiency in the ceramics shows a strong correlation between the transition rate and sintering temperature. Kinetics of phase transitions were studied by high temperature X-ray diffractometry (HTXRD) and differential scanning calorimetry methods. The reversible c-β phase transition was found to have very wide hysteresis (45-70°C), which depends on sintering temperature and density. Coefficients of thermal expansion of c- and β-phases were calculated from temperature dependence of lattice parameters obtained by HTXRD in the temperature range of 25-800°C. Microstructural changes on the surface of the cubic phase due to c-β phase transition studied by SEM and AFM.

An one-pot procedure was developed for the synthesis of mesoporous silica containing bimetallic PdCo using Pd(NO3)2 and CoCl2, and cetyl trimethyl ammonium bromide (CTAB) as the templating agent, and tetramethoxy silane (TMOS) as the precursor. The materials were characterized using high resolution scanning transmission electron microscopy (HRSTEM), elemental analysis, X-ray diffraction (XRD), and magnetic measurements. The data indicate that the bimetallic Pd-Co nanoparticles are uniformly distributed on the inner pore walls of silica. The magnetic measurements of reduced Pd-Co nanoparticles (4-5 nm) in mesoporous silica reveal a typical ferromagnetic behavior up to 20 K and exhibit superparamagnetic properties above 30 K.

Self-aligned arrays of long multi-walled carbon nanotubes (MWCNT) were grown by chemical vapor deposition (CVD) from a gas mixture of C2H4-H2-Ar-H2O at 750°C. A catalytically active alumina surfaces coated with a thin layer of iron and supported by a Si/SiO2 substrate were prepared using pulsed laser deposition method. Combinatorial approach has been used for optimization of catalytic properties of the multilayered system Si/SiO2/Al2O3/Fe. Sixteen different combinations of catalytic surfaces having thicknesses of Fe (0, 1, 2, and 3 nm), alumina (0, 10, 20 and 30 nm) per sample were deposited on two Si/SiO2 substrates with silica thickness 150 and 500 nm. To study the effect of alumina phase on efficiency of catalytic surfaces two substrate temperatures 200 and 700°C were used to produce amorphous and γ-alumina phases correspondingly. This approach allowed the optimal structure of catalytic surface to be determined from 64 different substrates on 4 samples in a single MWCNT growth experiment, for a given set of processing conditions. It was found that most efficient growth of MWCNT arrays on amorphous alumina occurred at Fe nanolayer thickness of 2 nm while catalyst having γ-alumina layer has tendency to be more efficient at higher thickness of Fe. Catalytic substrate containing amorphous alumina has less sensitivity to thickness of iron while γ-alumina based catalyst has significant variation in catalytic activity with change of iron content.

Highly aligned multi-walled carbon nanotube (MWCNT) arrays were synthesized on Si wafers. Water vapor was used to enhance the catalyst performance, which enabled continuous growth of MWCNT arrays for up to 3 hours. Various types of Fe patterning on a Si substrate with a multilayered structure were tested. MWCNT arrays up to 4 mm long were grown by Chemical Vapor Deposition (CVD). Environmental scanning electron microscopy was used to characterize the MWCNT morphology and showed that the nanotubes typically reveal a 20 nm outer diameter and 8 nm inner diameter. To investigate applications, a nanotube tower 1 mm × 1 mm × 4 mm in size was grown and peeled off the Si wafer. Each tower contains millions of individual nanotubes with 20–30 nm diameters. Electrochemical actuation of one MWCNT tower was demonstrated in a 2M NaCl solution. The MWCNT tower actuator operated up to 10 Hz without significantly decreasing strain. Only 1-2 volts was needed to obtain 0.2% strain. The aligned nanotube morphology of the tower is the reason for the high strain in the axial direction, which is an improvement compared to previously tested entangled buckypaper actuators. Cyclic voltammetry (CV) was performed to analyze the redox behavior of the nanotube tower used as an electrode. The CV response showed a sigmodal shape in a 6 mM K3(CN)6 ferrocyanide solution. This behavior provides ideal characteristics for biosensor development and application. Also, the measured electrical volume resistivity of the material was in the range of 0.1 ohm · cm. The overall improvement in the electrochemical actuation and electrical conductivity was much greater than previous nanocomposites obtained by dispersing powdered nanotubes into polymers. The demonstrated good properties suggest nanotube array towers can be considered a novel intelligent material.

This paper reports our recent work on the improved mechanical properties of alumina thin films with embedded Fe and Ni nanoparticle layers. The Fe/Ni nanoparticles-alumina composite thin films have been deposited using a multi-target pulsed laser ablation technique. Every film consists of 10 layers of alumina and 9 intermediate layers of Fe or Ni nanoparticles. Alumina layer thickness kept constant (∼22 nm) and total thickness of multilayered films was in range 220-280 nm depending on metal deposition time. Composite thin films were deposited at six different substrate temperatures in the range 200-800°C. The mechanical properties measurements, performed by nanoindentation in continuous stiffness mode and applying Nix-Bhattacharya (hardness H) and King's model (Young's modulus E) for film-only properties, have shown that pure alumina films deposited at temperatures 200-500°C are relatively soft (H = 15 GPa, E = 190 GPa), while films deposited at ≥600°C are significantly harder (H = 32 GPa, E = 320 GPa). Grazing incidence XRD (GIXRD) data indicated that γ-alumina peaks exist in high temperature samples while alumina films deposited at ≥500°C were amorphous. Embedding Ni and Fe nanoparticle layers at 500°C led to significant increase of H and E (31 GPa and 365 GPa with Fe and 33 GPa and 380 GPa with Ni) and appearance of γ-alumina peaks in GIXRD. Embedding on metal nanoparticle layers does not change mechanical properties of alumina films deposited at 200°C, and significant hardening of metal containing films starts at 400°C. These results suggest that metal nanoparticles have a catalytic effect on the growth of alumina thin films with enhanced crystallinty. The effect of Ni and Fe nanoparticle size on mechanical properties of thin films has been studied times at substrate temperature 500°C using eight different metal deposition. HRTEM data have shown that metal nanopartiles have uniform particle size distribution and inter-particle separation in the layer. Size of Ni and Fe nanoparticles with highest effect on mechanical properties was 4 -6 nm.

Pulsed laser deposition (PLD) technique was used to grow alumina (Al2O3) thin films on (100) silicon substrate under different deposition conditions. The relationship between Al2O3 thin film thickness, hardness, elastic modulus, surface morphology and PLD parameters such as laser energy and substrate temperature was investigated. The Film thickness was found to increase with an increase in laser energy and to decrease with an increase in substrate temperature. The film hardness and elastic modulus increases as substrate temperature increases. We have also shown that films are amorphous at lower substrate temperatures and transform to mixture of amorphous and crystalline phases. The ratio of amorphous to crystalline phases decreases with increase in temperature. The surfaces of Al2O3 film grown using PLD was found very smooth with least root square roughness less than 2 nm.

The tensile strengths of Nextel™ 720 fibers as well as tows and minicomposites made of these fibers were measured to study the effects of monazite coating at room temperature (RT) and 1200°C (HT). Tests were conducted on as-received materials (called unsoaked) as well as materials that had been thermally soaked at HT for 100 hours. Weibull analysis of fiber strength data shows close agreement between the Weibull modulus obtained from the statistical fracture distribution and the modulus obtained from a study of the gage length dependence of strength. The monazite coating does not change the RT strength of unsoaked single fibers, but has a beneficial effect in terms of strength retention under HT testing. This beneficial effect of the coating disappears for soaked samples. The results for tows and minicomposites also indicate that for the unsoaked condition, tensile failure appears to be driven by fiber surface flaws and the presence of the monazite coatings clearly improves both RT and HT strength of fibers, tows and minicomposites. However, the beneficial effects of the coating disappear after long term exposure to HT.

Liquid fuel combustion chemical vapor deposition technique was successfully used for YSZ thin film processing. The nucleation rates were obtained for the samples processed at different temperatures and total-metal-concentrations in the liquid fuel. An optimum substrate temperature was found for the highest nucleation rate. The nucleation rate was increased with the total-metal-concentration. Structural evolution of the thin film in the early processing stage was studied with regard to the formation of nuclei, crystallites and final crystals on the films. The films were found to be affected by high temperature annealing. The crystals and the thin films were characterized with scanning electron microscopy.