La2Zr2O7 (LZO) films have been grown by metalorganic decomposition (MOD) to be used as buffer layers for coated conductors. LZO can crystallize into two similar structures: fluorite or pyrochlore. Coated conductor application focuses on pyrochlore structure because it is a good barrier against oxygen diffusion. Classical x-ray diffraction is not able to separate the contribution of these two structures. Transmission electron microscopy and high-resolution transmission electron microscopy were used to determine the local distribution of these two phases in epitaxial LZO layers grown on LaAlO3. A characteristic feature of LZO thin films deposited by MOD is the formation of nanovoids in an almost single-crystal structure of LZO pyrochlore phase. For comparison, LZO layers deposited by metalorganic chemical vapor deposition were also studied. In this last case, the film is compact without voids and the structure corresponds to pyrochlore phase. Thus, the formation of nanovoids is a characteristic feature of MOD grown films.

The morphology of nanocolumns grown by glancing angle deposition is studied for molecular materials forming amorphous and crystalline solids. Amorphous tris(8-hydroxyquinoline)aluminum nanocolumn arrays were obtained at sample rotation speeds varying from 0.3 rpm (revolutions per minute) to 30 rpm. For crystalline pentacene, an array of regular nanocolumns formed at a rotation speed of 3 rpm, while higher and lower rotation speeds led to a wide distribution of column heights and shapes. The incoming molecular flux and the molecular diffusion length on column surfaces, both dependent on rotation speed, were found to govern the resulting morphology of crystalline pentacene nanocolumns.

We investigated the effects of gamma irradiation doses of 50, 100, and 103 kGy on boron-doped diamond (BDD) thin films synthesized using microwave plasma-assisted chemical vapor deposition with varying boron concentrations of [B]/[C]gas = 100, 1000, 2000, and 4000 ppm. The diamond thin films were characterized prior to and post-irradiation and the influence was assessed in terms of morphology, structure, and physical properties using scanning electron microscopy, atomic force microscopy, x-ray diffraction, vibrational spectroscopy (Raman and IR), x-ray photoelectron spectroscopy, and electrical measurement techniques. The results clearly showed that the response of gamma irradiation on BDD films was distinctive compared to those of undoped diamond films with changes in electronic behavior from metallic (>1019 to 1020 cm–3) to semiconducting (≤1019 cm–3), especially in the case of heavily boron-doped diamond films demonstrated by micro-Raman spectroscopy and electrical property characteristics. In fact, this modification in electrical property behavior induced by “gamma conditioning” can be effectively used to fine control boron doping in chemically vapor deposited diamond much needed for various electronic devices. The “gamma conditioning” refers to material processing by radiation which helps to passivate electrically active boron and defects with hydrogen migration thus fine tunes the boron acceptor concentration albeit that this is difficult to achieve during BDD film deposition. In addition, the results also indicate that almost all of the BDD films studied hereby tend to reach a state of damage saturation when submitted to gamma irradiation of 103 kGy. We discuss our novel findings in terms of the interplay of boron-hydrogen in diamond with possible multiple scenarios: (i) the generation of point/Frenkel defects due to Compton scattered electrons, (ii) the formation of a nonmetallic boron-rich borocarbide (e.g., B13C2) phase, (iii) the passivation of electrically active acceptor (B) sites due to the invariable presence of H in the grains and at the grain boundaries, (iv) the desorption of H from the diamond surface, and (v) the “priming or pumping” effect, which improves the electronic properties by compensating for the shallow boron acceptors to produce semiconducting/insulating material, verified by the cold neutron depth profiling technique.

Using a cold graphite mold casting method, bulk AlNiY chill-zone alloys were prepared at hypereutectic compositions with Al content from 85 at.% to 94 at.%. It was found that ultra-hard surface layers with a thickness of about 200 μm and submicron grain size form when the melt can be undercooled without heterogeneous nucleation at the mold contact surface. This hard chill-zone forming in contact with the mold possesses Vickers microhardness Hv about 350–420 and is thus harder than fully amorphous Al alloys. In compression, ultimate strength more than 1.1 GPa and true strain more than 150% without failure were achieved simultaneously. The combination of high strength and good plasticity will be discussed in relation to the special structure of the chill-zone alloy.

The mechanical behavior of electroplated Sn thin films was investigated using thermal-expansion induced strain. For stress above a threshold value, the stress relaxation observed during the thermal cycles is well-described by a power law creep mechanism with exponents similar to those of the bulk material. However, the stress relaxation showed significant thickness dependence so that the relaxation in thicker films is faster than thinner films. The surface oxide was also shown to have a considerable effect on retarding the relaxation by inhibiting diffusion to the surface. The relevance of the stress relaxation to whisker formation in Sn-based coatings is discussed.

The growth restriction factor is a parameter derived from binary phase diagrams and is a useful predictor for the grain refining response when a solute is added to a base alloy. This work investigates the relevance of growth restriction theory to titanium alloys where solidification rates are an order of magnitude faster than previous studies in aluminum- and magnesium-based systems. In particular, the segregation of Fe and Cr in titanium is investigated and the effects on grain size studied. It was found that the Scheil equation reasonably modeled solidification of titanium where cooling rates approach 120 °C/s, and the growth restriction factors for Fe and Cr were useful in predicting prior-β grain refinement. However, it was found that caution must be used when calculating growth restriction factors from binary phase diagrams.

A method allowing for the stable growth of carbon nanotubes (CNTs) on the surface of a fibrous metal mesh substrate (SUS304) was developed with the assistance of the microwave plasma-enhanced chemical vapor deposition process. The controlled addition of up to ∼13% of O2 to the CH4 plasma reacting gas flow was found to promote the growth of the CNTs by oxidizing the amorphous carbon and removing the active H2 radicals. However, excessive amounts of O2 (i.e., fraction of O2 > ∼13%) and H2 were found to play a negative role in the growth of the CNTs. The control of the density and length of the CNTs was also achieved by varying the H2 plasma reduction time and CH4 plasma reacting time, respectively. Longer H2 reduction pretreatment of the catalytic metal islands resulted in the formation of a less dense CNT forest with craters. When the growth time of the CNTs was increased to ∼20 min, their length was increased to ∼10 μm. However, when the growth time of the CNTs exceeded 20 min, their length was significantly decreased, indicating that the continuous presence of O2 in the CH4 plasma destroys the preformed CNTs due to the oxidation reaction.

The electrospray of a colloidal microemulsion (ME) solution and subsequent on-line annealing were used to produce barium titanate nanoparticles (BTO-NPs). The solvent of the ME solution (cyclohexane) was replaced with a high-conductivity solution (solute: ammonium acetate, solvent: tetrahydrofurfuryl alcohol, conductivity: 3.1 × 10−2 S/m) to generate ultrafine droplets during the electrospraying. Well-dispersed and well-crystallized BTO-NPs with a perovskite structure were successfully fabricated at an annealing temperature of 1173 K. The size distribution of the BTO-NPs was successfully measured by applying a differential mobility analyzer and condensation nucleation counter to nanoparticles in-flight. The average size of the BTO-NPs was controlled within a range of 15 to 25 nm by changing the feeding rate. The electrospray of an ME solution with lower conductivity (solvent: 1-octanol, conductivity: 7.0 × 10−4 S/m) yielded amorphous particles with larger particle sizes. Thus, the electrospray of a high-conductivity solution is required to fabricate well-crystallized and dense BTO-NPs with smaller particle sizes.

A novel dispersant “mono-2-(methacryloyloxy)ethyl succinate” was formulated for dispersing 30-nm SiC nanoparticles in vinyl ester resin. The eight carbon rule was used as the guideline to achieve a particle–particle separation of 20 to 60 nm for colloid stability. Fourier transform infrared spectroscopy was performed to characterize the SiC particle surfaces. Only a negligible amount of oxidized layer was observed; which illustrates that the SiC surface is basic. Thus, the Lewis base-Lewis acid reactions make the functional group –COOH an effective adsorbate to the SiC nanoparticle surface. The organofunctional group “methacrylates,” which exhibits the best wet strength with polyester copolymerizes with styrene monomers in the vinyl ester during cure. Hence, this novel dispersant also acts as an efficient coupling agent that reacts with both SiC and vinyl ester. The monolayer coverage dosage of 62 fractional wt% of the dispersant was used to attain the minimum filled resin viscosity. The multicomponent compositional imaging using atomic force microscopy confirmed the monodisperse SiC nanoparticles in vinyl ester. The 3 vol% SiC reinforced vinyl ester achieved a 75% increase in modulus, 42% increase in strength, and 75% increase in toughness as compared with the neat resin without nanofiller reinforcement.

The in situ x-ray diffraction observations of the bainitic transformation were conducted by using the high-temperature x-ray diffraction technique. The volume fraction and carbon content of austenite depend on the transformation temperature. The d{110} value of bainitic ferrite decreases with increasing austempering temperature, which is related to the decrease of carbon concentration in bainitic ferrite. Asymmetry diffraction peaks are obtained for samples at the early stage of transformation at any austempering temperatures. This asymmetry diffraction peak after the formation of bainitic ferrite could be attributed to a heterogeneous distribution of carbon in different regions of austenite and show that two types of austenite with different carbon contents, low-carbon austenite (γLC) and the high-carbon austenite (γHC), exist during the transformation. The microstructure after cooling down to room temperature is presented to show the effectiveness of the x-ray diffraction analysis.

One embodiment of YBa2Cu3O7-x (YBCO)-coated conductors consists of YBCO film grown using a metal-organic deposition (MOD) process on a buffer layer stack deposited on a Ni-W substrate. A possible alternative is to replace the multilayer buffer stack with a single layer of LaMnO3 (LMO) grown by MOD. A suitable temperature (T) – oxygen partial pressure (PO2) process-window to grow LMO films via MOD on Ni substrates has been identified. Untextured LMO was grown on pure Ni. However, we have not been able to grow phase-pure LMO films on either bare or Y2O3-coated, biaxially textured Ni-5W (at.%) due to the incongruent, overlapping requirements of having the PO2 low enough to not oxidize the Ni-5W substrate but high enough to convert the metal-organic precursors to LMO and the relatively high temperatures needed to form an epitaxial film in an MOD process. The main problem is that tungsten from the substrate reacts with cations in the overlying film forming tungstates when the films are processed in the T-PO2 window.

Pb(Mg1/3,Nb2/3)O3-PbTiO3 (PMN-PT, 43% PT) thin films have been developed by modified sol-gel processing with polyvinylpyrrolidone (PVP) as a modifier and lead nitrate as a lead source. With PVP modification, perovskite phase was directly crystallized from amorphous film matrix at a temperature as low as 430 °C, and the crystallinity was significantly enhanced. Kinetics studies show that the crystallization process is controlled by heat transfer phenomena at the annealing temperatures ≤460 °C. At higher annealing temperatures (550–700 °C), it is a diffusion-controlled reaction with an activation energy of 167.7 kJ/mol, almost two times lower than that for the films without PVP modification. The promotion mechanism of perovskite crystallization by PVP addition has been discussed accordingly. The resultant films consisted of nanocrystallines and exhibited relaxor-like dielectric behavior, although the composition of the films located in normal ferroelectrics.

Polycrystalline manganites within the compositional variation La0.72(Ca1−xSrx)0.28MnO3 (x = 0, 0.25, 0.50, 0.75, 1.0) were synthesized by solid-state reaction method. An initial orthorhombic structure was observed at x = 0, with a subsequent change to rhombohedral structure for x ≥ 0.25. The Curie temperature of the compounds exhibited a marked dependence with the Sr content, with general variations between 190 K (x = 0) and 364 K (x = 1.0), while the saturation magnetization at room temperature showed a small variation between the range 0.30 and 0.38 T. The magnetocaloric effect, measured through heat capacity experiments, showed a maximum entropy variation of −2.56 J/kg · K at x = 0.25, besides a maximum adiabatic temperature variation of 1.13 K. Results are interpreted in terms of the structural transition observed and its effect on the radius of the A-site of the perovskite structure.

Vanadium oxide thin films were deposited using pulsed direct current (dc) magnetron sputtering in an atmosphere containing argon and oxygen. The total pressure was varied from 2.5 to 15 mTorr, and the oxygen-to-argon ratio was varied from 2.5 to 30%. The resulting films were characterized using Rutherford backscattering spectroscopy (RBS), transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), and glancing incidence x-ray diffraction (GIXRD). Electrical resistivity was calculated from I–V curves acquired from two-point-probe measurements and thicknesses measured from bright-field TEM images of cross-sectioned samples. TEM and GIXRD were used to characterize the crystallinity of each film. A transition from nanocrystalline to amorphous growth was observed with increasing partial pressure of oxygen. In all samples, the only crystalline phase observed was cubic vanadium oxide with the sodium chloride structure. Though the cubic VOx equilibrium phase field is limited to a maximum of x = 1.3, the cubic phase was observed with a value of x up to 2 in the present work. It was apparent from electron diffraction data that increased oxygen content correlated with an increase in the film disorder. The increase in oxygen content also corresponded with an increase in the film resistivity, which varied over 7 orders of magnitude from 1.18 × 10−3 to 2.98 × 104 Ω·cm. The temperature coefficient of resistance was found to increase with increasing oxygen content from −0.1 to −3.5%/°C. A direct correlation between film disorder and temperature coefficient of resistivity (TCR) was observed and could be exploited to engineer materials with the desired TCR.

To study both the effect of Ag and the relative density on the elastic properties of nanoporous Au (np-Au) foams, partially as well as fully dealloyed np-Au samples with various ligament sizes were prepared. Additionally, Ag-coated np-Au samples were synthesized by immersing np-Au in a 1 M Ag nitrate solution, followed by drying and thermal decomposition of the deposited Ag nitrate salt to Ag, NO2, and O2. Cross-sectional analysis revealed that this method yields a homogeneous Ag distribution and that the Ag concentration can be adjusted within the range of 0 to 20 at.%. Mechanical testing was performed by depth-sensing nanoindentation. It was observed that the effect of the relative density on the elastic properties of np-Au seems to be much stronger than predicted by the Gibson and Ashby relationship: Even Ag contents as low as 1 at.% can significantly change the modulus values. On the other hand, the elastic modulus of np-Au seems to be independent of the ligament size.

Exchange bias phenomena of amorphous CoFeSiB ribbons have been probed at room temperature. The dramatic loop shift away from zero point occurred when the ribbons were annealed in ambient atmosphere with longitudinal field. The possible crystalline phases grown in our ribbons are discussed based on the grazing incidence diffraction and energy dispersive x-ray spectroscopy. The magnetic domain configuration of ribbon surface was also observed to make clear the dependence of bias behavior on the induced magnetic anisotropy in the ribbon. A simple phenomenological explanation was given to discuss the exchange bias in ribbons.