Conventional and high-resolution electron microscopies were used to investigate the microstructure and precipitation mechanism of four kinds of γ′–Fe4N nitrides, formed at the surface during nitriding of polycrystalline pure iron sheet. γ′ nitrides in the top columnar compound layer were thin plates (3–12 nm), which precipitated from ε–Fe2−3N grains with orientation relationship of (111)γ′//(0001)ε and [011]γ′//[1210]ε. Those in the transition compound layer remained as equiaxed grains (1–1.5 μm), which grew from the α–Fe substrate during nitriding. In the diffusion layer, striated γ′ nitrides nucleated from α″–Fe16N2 nitrides with orientation relationship of (100)γ′// (110)α″ and [011]γ′//[111]α″ while unstriated γ′ nitrides precipitated from the α–Fe substrate with the orientation relationship of (100)γ′//(110)α and [011]γ′//[111]α.

Fluorphlogopite mica crystallites of dimensions in the range 0.5 to 24 µm were grown within silicate glass of suitable compositions by heat treatment at 1168 K. After an ion exchange treatment (K+ ⇆ Ag+) the specimens were subjected to an electrodeposition reaction. With the optimum concentration of K+ ions in the precursor glass, electrodeposition brought about the growth of silver nanowires about 0.5 nm diameter within the nanochannels of the fluorphlogopite mica structure. By applying a voltage pulse of 20 volts of duration 3 s, break junctions could be induced in the nanowires. A high dielectric constant of around 1.0 × 107was found in the resultant specimen. This was shown to be quantum mechanical in origin and arose due to the presence of metal filaments about 1280 nm in length. An asymmetric voltage–current characteristic was recorded at 114 K in the case of the specimen containing silver nanowires grown within the mica structure. This is believed to arise due to formation of a nanojunction between the metal nanowire and silver nanoparticles with diameters of less than 3 nm. The latter were earlier shown to behave as insulators

A commercially available aromatic polyimide film Kapton H 25-μm thick was heat-treated at temperatures between 490 and 540 °C in a nitrogen flow. Magnetization was measured as a function of magnetic field at 5 and 300 K and function of temperature in a field of 1 T. Diamagnetic and paramagnetic components were observed for all heat-treated films. Ferromagnetism was discovered even at 300 K in the films heat-treated at 490–520 °C. The saturation magnetization, coercive force, and residual magnetization for the 520 °C treated film were 0.059 J T−1 kg−1, 0.004 T, and 9 × 10−4 J T−1 kg−1, respectively, at 300 K. The ferromagnetism has been maintained 5 months after. Original Kapton H and the heated films were found to contain no metallic elements. The ferromagnetism should be caused by a long-range magnetic spin ordering of unpaired electrons located on slightly decomposed imide molecules with defects or on intermediates with free radicals formed by thermal decomposition. The ordering is probably established three dimensionally throughout the heat-treated films with a structural regularity similar to that of the original Kapton H.

We used the topology optimization technique to obtain two-dimensional, isotropic cellular solids with optimal effective elastic moduli and effective conductivity. The overall aim was to obtain the best (simplest) manufacturable structures for these effective properties, i.e., single-length-scale structures. Three different but simple periodic structures arose due to the imposed geometric mirror symmetries: lattices with triangular-like cells, hexagonal-like cells, or Kagomé-like cells. As a general rule, the structures with the Kagomé-like cells provided the best performance over a wide range of densities, i.e., for 0 ≰ ф <0.6, where ф is the solid volume fraction (density). At high densities (ф > 0.6), Kagome-like structures were no longer possible, and lattices with hexagonal-like or triangular-like cells provide virtually the same optimal performance. The Kagomé-like structures were found to be a new class of cellular solids with many useful features, including desirable transport and elastic properties, heat-dissipation characteristics, improved mechanical strength, and ease of fabrication.

An investigation of the effects of the iron defect k in LiZnTiMn ferrites using Mössbauer spectroscopy and ferromagnetic resonance techniques was carried out in single-phased samples. Results show that the isomer shifts have values corresponding to a compound with either low-spin Fe(II), low-spin Fe(III), or high-spin Fe(III). On the other hand, the Lande factor and the ferromagnetic resonance linewidth disclosed that g is always very close to 2, being equal to 2.02 when k = 0.06. A minimum in ΔH was detected for this value of k. From these results, the possible presence of Fe2+ in the samples could be excluded, and it was concluded that the changes in ΔH are due to the variation of the Fe(III) contents in the tetrahedral and octahedral sites. The existence of the minimum in ΔH is due to a compensation point in the magnetocrystalline anisotropy.

Nanoembedded aluminum alloys with bimetallic dispersoids of Sn and Pb of compositions Sn82–Pb18, Sn64–Pb36, and Sn54–Pb46 were synthesized by rapid solidification. The two phases, face-centered-cubic Pb and tetragonal Sn solid-solution, coexist in all the particles. The crystallographic relation between the two phases and the matrix depends upon the solidification pathways adopted by the particles. For Al–(Sn82–Pb18), we report a new orientation relation given by [011]Al//[010]Sn and (o11)A1//(101)Sn. Pb exhibits a cube-on-cube orientation with Al in few particles, while in others no orientation relationship could be observed. In contrast, Pb in Sn64–Pb36 and Sn54–Pb46 particles always exhibits cube-on-cube orientation with the matrix. Sn does not show any orientation relationship with Al or Pb in these cases. Differential scanning calorimetry studies revealed melting at eutectic temperature for all compositions, although solidification pathways are different. Attempts were made to correlate these with the melting and heterogeneous nucleation characteristics.

Thin films of poly(methyl methacrylate)–multiwalled nanotubes composites were produced by spin coating using different nanotube concentrations. The materials were characterized by scanning electron microscopy, energy-dispersive x-ray analysis, and Raman spectroscopy to obtain information on the possible interactions between the constituents and to control the homogeneity of the films. Electrical conductivity measurements of the composites, as a function of the nanotube concentration, show a percolation threshold at very low concentration. Also, the J–E characteristics exhibits a nonlinear behavior at low concentration, becoming linear far above the threshold.

We investigated effects of postdeposition heat treatment (HT) on the properties of plasma polymer films deposited by plasma-enhanced chemical vapor deposition using a mixture of decahydronaphthalene and tetraethyl orthosilicate as the precursors, which were referred to as plasma-polymerized decahydronaphthalene:tetraethyl orthosilicate (PPDHN:TEOS) films. HTs at 350, 450, and 500 °C decreased the relative dielectric constant k of the PPDHN:TEOS films from 3.16, the k value of the as-deposited film, to 2.82, 2.72, and 3.02, respectively. The change of k value as a function of HT temperature was correlated with the change of Fourier transform infrared absorption peaks of O–H, C = O, and Si-related groups. As the HT temperature increased, the thermal stability of the PPDHN:TEOS film increased. PPDHN:TEOS films, as-deposited or heat treated, showed leakage current density in the order of 10−7 A/cm2 at 1 MV/cm.

Gas-atomized Ni powders were mechanically milled under liquid nitrogen and subsequently sprayed using a high-velocity oxygen-fuel thermal spraying system. The resultant coatings were evaluated using various analytical methods, including scanning electron microscopy (SEM), transmission electron microscopy, and atom probe field ion microscopy (APFIM). The results indicated that the majority of the grains in nanocrystalline Ni coating were equiaxed with an average grain size of 50 ± 23 nm. SEM elemental dot mapping analysis suggested that oxide particles were distributed along the prior droplet boundaries and interpass boundaries in the coatings. The APFIM analysis indicated that the distribution of oxygen was very inhomogeneous in the nanocrystalline coating samples studied. Mostly small NiO precipitates with a size range of 1–7 nm were found throughout the grains, and the average size of these precipitates was approximately 4 nm. However, large oxide precipitates with a size up to 55 nm were also observed. In addition, increased amounts of oxygen were found at the grain boundaries and at structural defects.

The interfacial reactions between aluminosilicate ceramics doped with MgO, CaO, or BaO and Al–7 wt% Si alloy were investigated at 1023, 1173, and 1323 K under vacuum for 4 h. Alkaline-earth oxide additives defined phase formation and microstructure of the sintered ceramics and subsequently controlled the ceramic/metal interfacial reactions, which were always intensive. In general, reaction zones consisted of Al2O3, infiltrated with Al. In the case of CaO- and BaO-doped ceramics, precipitates formed into the metal phase and concentrated the reduced Ca and Ba, respectively. A reaction mechanism is proposed, which anticipates an active role of SiO2.

Small-punch tests were conducted at 4, 77, and 293 K on three newly developed cryogenic austenitic stainless steels, JN1, JJ1, and JK2, which were solution treated, water-quenched, and then aged at 923, 973, 1023, and 1073 K for 5 h. Small-punch test energy was employed for the evaluation of the aging-induced embrittlement behavior in these materials. An SEM analysis of the fracture surface for the solution-treated steel specimens indicated a ductile fracture, having the highest SP test energy values. On the contrary, intergranular brittle fracture was observed in aged specimens. The small-punch test energy of materials decreased significantly as the aging process progressed. The highest and lowest decrease in small-punch test energy with aging temperature occurred in JN1 and JK2 steels, respectively. The decrease in small-punch test energy was shown to follow appropriately the aging-induced embrittlement in these materials. The difference in aging-induced embrittlement behavior for these steels was explained on the basis of the volume fraction of intergranular precipitates in aged samples.

Hardness and elastic modulus of (111), (110), and (001) oriented Ni3Al single crystals were determined by nanoindenter measurements. Obvious elastic modulus anisotropy and hardness anisotropy were observed. The modulus for (001) was about 17% smaller than that for (111), (110). The hardness was found to be strongly dependent on the indentation size and exhibited a small anisotropy at low indentation loads. When the indentation load was increased further, the hardness anisotropy became apparent. The hardness for (111) was observed to be higher compared to (001). The indentation hardness size effect was examined by using strain gradient plasticity theory.

Pb(Mg1/3Ta2/3)O3 (PMT) powders and heteroepitaxial thin films on (001) SrTiO3 (STO) substrates were prepared by the chemical solution deposition method. The phase development in PMT powders and thin films was investigated by x-ray diffraction, and the microstructure of PMT thin films was studied by transmission electron microscopy. Phase transformation from pyrochlore to perovskite in the PMT powder samples occurred in the temperature range of 700–800 °C, and perovskite phase was mainly observed in samples annealed above 800 °C. However, perovskite phase in PMT thin films on STO substrates was formed mainly in samples annealed as low as 750 °C/1 h, and it shows an epitaxial orientation relationship of [100](001)PMT∥[100](001)STO.

A high degree of texture was observed in melt-spun Sm(Co0.68Fe0.22Cu0.08Zr0.02)7.7 ribbons prepared by single-roller melt spinning at low wheel speed; their easy magnetization axis was parallel to the ribbon plane. Magnetization studies showed an obvious magnetic anisotropy and a 90% higher remanance in ribbons for the field parallel to the longitudinal direction (8.5 kGs) than that for the field parallel to the wide direction (4.4 kGs); this was attributed to a dendritic structure of needle-size grains (2–3 × 10–40 μm) with their long axis parallel to the ribbon plane. This texture allowed the development of a new process for producing anisotropic permanent magnets. The domain structure was studied by magnetic-force microscope. A highly ordered and strip-shaped magnetic domain structure was observed on the surface of the ribbons. This was due to the preference for tetragonal c-axis orientation parallel to the surface of melt-spun ribbons. We calculated the domain wall energy γ and critical single-domain particle size Dc of Sm(Co0.68Fe0.22Cu0.08Zr0.02)7.7 ribbons.

The dynamic piezoelectric response of SrBi4Ti4O15 ceramics with Aurivillius structure was investigated at high alternating stress, low frequencies (0.01 to 100 Hz), and temperatures from 20 to 200 °C. The piezoelectric nonlinearity, observed only at high pressures (>10 MPa) and elevated temperatures (>150 °C), is interpreted in terms of contributions from non-180° domain walls. At weak fields, the frequency dependence of the longitudinal piezoelectric coefficient was explained in terms of Maxwell–Wagner piezoelectric relaxation. The Maxwell–Wagner units are identified as colonies that consist of highly anisotropic grains which sinter together, and whose distribution in the ceramic is strongly dependent on sintering conditions.

We synthesized carbon tubule nanocoils by catalytic thermal chemical vapor deposition. The iron catalyst necessary in the growth of carbon nanocoils was prepared only by coating the iron compound solution on indium tin oxide–coated glass substrate. It was found that the iron compounds have the same catalytic function as iron thin film prepared by evaporation or electroplating. Furthermore, the density of the prepared carbon nanocoils could be easily controlled by changing the density of the solution of iron compounds. In addition, the poly(methylphenylsilane) proved to be an excellent dispersive medium for the iron compound in preparation of the carbon nanocoils in desired densities.

To improve the oxidation resistance of Si3N4 material, a dense and continuous layer, composed of small Y2Si2O7 crystallites and silicate glass, was formed on the surface. The surface layer was formed by exposing the specimens in a flowing H2 atmosphere containing 0.1% H2O at 1450 °C for 1 h. For the purpose of comparison, specimens of the same material were heat treated in air at 1450 °C for 1 h. Small equiaxed Y2Si2O7 crystallites were formed when the specimen was heat treated in the wet H2 atmosphere, while relatively large and elongated Y2Si2O7 crystallites developed when the specimens were heat treated in air. The oxidation resistance of Si3N4 material was improved remarkably by the heat treatment in the wet H2, while no improvement in oxidation resistance was observed from the specimen heat treated in air. The improvement was attributed to the retardation of the transport of oxidants through the dense and continuous layer formed on the surface.

Crystals of CaAl4O7 (space group C2/c) have been examined by high-temperature powder x-ray diffractometry to determine the change in unit-cell dimensions with temperature up to 1473 K. The lattice deformation induced by thermal expansion has been investigated by matrix algebra analysis to determine the directions and magnitudes of the principal distortions. During heating from 298 K, two of the three principal distortions, λ1 and λ2, invariably showed a positive thermal expansion, the magnitudes of which at 1473 K are respectively approximately 1.0% and approximately 0.8%. The direction of λ1 was nearly parallel to [304], and the λ2 axis invariably coincides with the crystallographic b axis. On the other hand, the distortion λ3 showed a negative thermal expansion below approximately 1173 K; the maximum contraction of approximately 0.2% occurred at approximately 673 K nearly along [207]. During further heating to 1473 K, λ3 showed, to the contrary, a positive expansion of approximately 0.2% nearly along [50, 16]. The negative thermal expansion along the λ3 axis substantially accounts for the mean linear thermal expansion being very low at temperatures below approximately 473 K.

A series of Ti–Si–N coatings with 0 < Si < 20 at.% were synthesized by inductively coupled plasma assisted vapor deposition. Coating composition, structure, atomic short-range order, and mechanical response were characterized by Rutherford backscattering spectrometry, transmission electron microscopy, x-ray absorption near-edge structure spectroscopy, and instrumented nanoindentation. These experiments show that the present series of Ti–Si–N coatings consists of a mixture of nanocrystalline titanium nitride (TiN) and amorphous silicon nitride (a-Si:N); i.e., they are TiN/a-Si:N ceramic/ceramic nanocomposites. The hardness of the present series of coatings was found to be less than 32 GPa and to vary smoothly with the Si composition.

Arrays of Cu/Cu2O nanowires were grown by electrodeposition in the nanopores of track-etched polymer membranes. If an appropriate solution is used, the electrode potential spontaneously oscillates during the application of a constant cathodic current. Both the period of the oscillations and the composition of the nanowires can be controlled by varying the applied current density. A nanocomposite of copper and cuprous oxide is deposited at an applied current over which oscillations occur. In contrast, pure Cu or Cu2O nanowires are obtained at a deposition current out of the range of oscillation. Electrical transport measurements were also performed on these nanowires.