The growth mechanisms of MgB2 films obtained by different methods on various substrates are comparably studied by transport measurements and scanning electron microscopy observations. The analyzed films include those prepared by ex situ postanneal with Tc0 ˜38.8 K and those from in situ anneal with Tc0 ˜24 K. It is clearly observed that the films obtained by the high-temperature reaction of e-beam evaporated B with Mg vapor are formed by the nucleation of independent MgB2 grains at the film surface, indicating that this approach may not be suitable to obtain epitaxial films. A significant oxygen contamination was also present in films obtained from pulsed-laser-deposition-grown precursors, which drag the Tc0 down to 24 K.

The transformation to perovskite phase of Pb0.91La0.09Zr0.65Ti0.35O3 (9/65/35) films on r-sapphire and resulting annealed microstructures were examined by transmission electron microscopy. A random equiaxed polycrystalline grain morphology (approximately 600 nm) was observed after rapid-thermal annealing or furnace annealing when the as-deposited (radio-frequency-magnetron sputtering) films were predominantly pyrochlore. However, an interesting paired-plate structure was revealed after furnace annealing when the as-deposited films were fully perovskite. The average size of such a split precipitate was 35 nm in width and 150 nm in length.

When bulk ferromagnetic Fe80P13C7 amorphous rods of approximately 2-mm diameter are compacted together in a hot press, a variety of different microstructures, depending on the experimental conditions, are produced. The most intriguing microstructure is that two different bulk amorphous rods can be fused together perfectly at a temperature of 683 K and under a pressure of 2.5 to 4 GPa for a period of 5 min.

Yttrium iron garnet (YIG) powder has been synthesized in just less than 10 min in a multimode microwave oven operating at 2.45 GHz. The simple solid-state synthesis involves an anisothermal reaction between a highly microwave absorbing Fe3O4 and a low microwave absorbing Y2O3 at temperatures of 1300 °C. The rapidity of the YIG formation suggests that the reaction rate is possibly enhanced by several times in a microwave field.

A novel and fast microwave route is described for the synthesis of yttrium aluminum garnet (YAG) and for its sintering to translucent bodies. Precursor was made by microwave decomposition (20 min) of aluminum tri-sec-butoxide and yttrium nitrate dissolved in ethyl acetate. The precursor, conventionally calcined at 1000 °C (1 h), was sintered in microwave using SiC as secondary heater for just 35 min. Resulting translucent YAG has a microhardness (HV) of 18.1 GPa and fracture toughness (KIC) of 4.3 MPa m1/2. A 0.86-mm-thick sintered pellet exhibits approximately 45% transmission for 520-nm radiation. The entire microwave process requires less than 3 h.

Silicon microwires have been synthesized by the Taylor microwire process. In this process, silicon is melted inside a glass tube by a local heating source and fine microwire is then drawn out by mechanical pulling. The silicon microwire is encapsulated in a silica glass coating. Flexible 10–25-μm diameter polycrystalline silicon microwires were synthesized by this method in continuous lengths up to 460 mm.

A family of lanthanide silicates adopts an oxyapatitelike structure with structural formula Ln9.33 0.67(SiO4)6O2 (Ln = La, Sm, Nd, Gd,   = vacancy). The enthalpies of solution, ΔHS, for these materials and their corresponding binary oxides were determined by high-temperature oxide melt solution calorimetry using molten 2PbO B2O3 at 1078 K. These data were used to complete thermodynamic cycles to calculate enthalpies of formation from the oxides, ΔH0 f-oxides (kJ/mol): La9.33 0.67(SiO4)6O2 = 776.3 ± 17.9, Nd9.33 0.67(SiO4)6O2 = 760.4 ± 31.9, Sm9.33 0.67(SiO4)6O2 = 590.3 ± 18.6, and Gd9.33 0.67(SiO4)6O2 = 446.9 ± 21.9. Reference data were used to calculate the standard enthalpies of formation from the elements, ΔH0 f (kJ/mol): La9.33 0.67(SiO4)6O2 = 14611.0 ± 19.4, Nd9.33 0.67(SiO4)6O2 = 14661.5 ± 32.2, Sm9.33 0.67(SiO4)6O2 = -14561.7 ±; 20.8, and Gd9.33 0.67(SiO4)6O2 = -14402.7 ± 28.2. The formation enthalpies become more endothermic as the ionic radius of the lanthanide ion decreases.

A new synthesis route, based on internal oxidation reactions in multiphase alloys, is proposed for the controlled production of near-surface, complex ceramic-ceramic or ceramic-metallic composite structures. Using this approach, a microdispersion of a complex nitride perovskite, Cr3PtN, was formed in Cr2N or Cr(Pt) by internal nitridation of a two-phase Cr(Pt) + Cr3Pt precursor alloy. A framework for use of this phenomenon to synthesize island micro- (and potentially meso- or nano-) composite functional surface structures is presented.

Changes in mass density of amorphous Pd80Si20 were monitored in situ during irradiation with He2+ and H+ ions at temperatures below 100 K and during subsequent thermal treatment. The mass density decreased with increasing ion fluence and exponentially approached a saturation value of −1.2%, corresponding to a recombination volume of 190 atomic volumes. The initial swelling rate was 2.3 atomic volumes/displaced atom. The mass density of the irradiated material increased during subsequent thermal treatment, and the irradiation-induced decrease of the mass density recovered completely at room temperature.

A solid polythiophene pellet was ablated by a KrF excimer laser beam to deposit thin films on silicon substrates. The laser-ablated plasma was studied by optical emission spectroscopy to identify the photon-breaking of C–S bonds in the ablated heterocycles. Raman and x-ray photoelectron spectroscopy measurements of the deposited thin films also supported the selective photon-induced bond breaking. After eliminating sulfur in the molecular structures, the thin films appeared to be composed of cubic nanocrystals with a uniform size of 240 nm. X-ray diffraction measurement determined the cubic crystal structures with a lattice constant of α =3.38 Å and suggested a quasi-onedimensional carbon chain structure along the body diagonal of the cube.

The fracture behavior upon stable crack propagation in bending was investigated for a ceramic matrix composite comprising 15 vol% of calcium hexaluminate (CaAl12O19 or “CA6”) in an Al2.O3 matrix and compared to the crack bridging stresses as measured by microprobe fluorescence spectroscopy. In addition, piezospectroscopy coefficients of -4.57 and -3.79 cm-1 GPa-1 were determined for the peaks located at 14488 and 14528 cm-1, respectively, for monolithic CA6. It was concluded that the macroscopic R-curve behavior of the composite could be predicted from microscopic bridging stress data and indicated microprobe fluorescence spectroscopy to be a significant experimental tool for the investigation of fracture micromechanisms in ceramic materials.

A simple and convenient solvothermal reaction has been developed to produce CuInS2 nanorods and nanotubes from the elements in ethylenediamine at 280 °C. The products were characterized by x-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, scanning electron microscopy, and x-ray photoelectron spectroscopy. Analysis shows that the coordinating ability of ethylenediamine and the existence of liquid In may play important roles in the growth of one-dimension nanocrystallites and the electron-transfer reaction. In addition, spherical CuInS2 micrometer particles were obtained at 350 °C.

Dielectric response of mesoporous silica films was monitored as a function of several gas-phase chemical species. The effects of humidity, ammonia, and methane on dielectric constant and dissipation factor of films subjected to different chemical treatments are described. Dielectric constant and dissipation factor of partially dehydroxylated films were found to be highly sensitive to both water vapor and ammonia in air. The capacitive devices based on mesoporous silica films show potential for use in chemical sensors.

ZnO-based varistor samples with a relatively high Sb2O3 to Bi2O3 ratio of 5 were fired at 1200 °C and found to have a high threshold voltage (VT) of 280 V/mm and a low energy-absorption capacity of 50 J/cm3. The introduction of rare-earth oxides (REO) increased the energy-absorption capacity of Pr6O11- and Nd2O3-doped samples to 110 J/cm3 while their threshold voltage (VT) remained slightly above 300 V/mm. Doping with Pr6O11 and Nd2O3 altered the formation of the spinel phase and significantly changed its particle size and distribution which, as a result, had a positive effect on the energy-absorption capacity of the REO-doped samples. Doping with small amounts of Pr6O11 and Nd2O3 appears to be promising for the preparation of ZnO-based varistors with a high breakdown voltage and a high energy absorption capacity.

The standard enthalpy of formation of InN at 298 K has been determined using high-temperature oxidative drop solution calorimetry in a molten sodium molybdate solvent at 975 K. Calorimetric measurements were performed on six InN samples with varying nitrogen contents. The samples were characterized using x-ray diffraction, chemical analysis, electron microprobe analysis, and Brunauer–Emmett–Teller surface area measurement. The variation of the enthalpy of drop solution (kJ/g) with nitrogen content is approximately linear. The data, when extrapolated to stoichiometric InN, yield a standard enthalpy of formation from the elements of ?28.6 ± 9.2 kJ/mol. The relatively large error results from the deviation of individual points from the straight line rather than uncertainties in each set of data for a given sample. This new directly measured enthalpy of formation is in good agreement with the old combustion calorimetric result by Hahn and Juza (1940). However, this calorimetric enthalpy of formation is significantly different from the enthalpy of formation values derived from the temperature dependence of the apparent decomposition pressure of nitrogen over InN. A literature survey of the enthalpies of formation of III–N nitride compounds is presented.

Samples of Co clusters embedded in a carbon fiber matrix have been prepared using a heat-treatment method of cellulose fibers with ion-absorbed cobalt cations. Depending on the heat-treatment temperature used, different cluster sizes have been obtained, ranging from superparamagnetic clusters (average size 10 nm) to ferromagnetic nanoparticles (size between 30 and 200 nm). The formation of graphite planes surrounding the nanoparticles has been observed.

High-strength Cu-based bulk glassy alloys were formed in the Cu–Hf–Ti system by the copper mold casting and melt clamp forging methods. The maximum diameter is 4 mm for the Cu60Hf25Ti15 alloy. The substitution of Hf in the Cu60Hf40 alloy by Ti causes an increase in the glass-forming ability (GFA). As the Ti content increases, the glass transition temperature (Tg) decreases, while the crystallization temperature (Tx) shows a maximum at 5% Ti and then decreases, resulting in a maximum supercooled liquid region ΔTx (= Tx − Tg) of 78 K at 5% Ti. The liquidus temperature (T1) has a minimum of 1172 K around 20% Ti, and hence, a maximum Tg//T1 of 0.62 is obtained at 20% Ti. The high GFA was obtained at the compositions with high Tg/T1. The bulk glassy alloy exhibits tensile fracture strength of 2130 MPa, compressive fracture strength of 2160 MPa, and compressive plastic elongation of 0.8 to 1.6%. The new Cu-based bulk glassy alloys with high Tg/T1 above 0.60, high fracture strength above 2100 MPa, and distinct plastic elongation are encouraging for future development as a new type of bulk glassy alloy that can be used for structural materials.

Cracks induced by 0.049N load indentation on the surface of gallium arsenide single crystal were investigated before and after annealing. The results revealed that the crack initiation essentially relates to the shear deformation during indentation. There were dislocation generation, lattice distortion, and the transformation from crystalline to disordered structure, leading to the occurrence of an amorphous band in front of the crack tip. After being annealed at 500 °C for 60 min, the amorphous band disappeared, and instead, recrystallized grains appeared along the crack-propagation direction. It is reasonable to propose that crack propagation is the result of the decohesion of the amorphous band rather than the direct debonding along a certain atomic plane.

In this paper, a unique processing approach for producing a tailored, externally controlled microstructure in zinc oxide using very high heating rates (to 4900 °C/min) in a microwave environment is discussed. Detailed data on the densification, grain growth, and grain size uniformity as a function of heating rate are presented. With increasing heating rate, the grain size decreased while grain size uniformity increased. At extremely high heating rates, high density can be achieved with almost complete suppression of grain growth. Ultrarapid microwave heating of ZnO also enhanced densification rates by up to 4 orders of magnitude compared to slow microwave heating. The results indicate that the densification mechanisms are different for slow and rapid heating rates. Since the mechanical, thermal, dielectric, and optical properties of ceramics depend on microstructure, ultrarapid heating may lead to advanced ceramics with tailored microstructure and enhanced properties.

Ba4Nd2Ti4Ta6O30 dielectric ceramics with high-Ε and low dielectric loss were modified to improve the temperature coefficient of dielectric constant. Through partial substitution of Ti4+ for Ta5+, a significantly reduced temperature coefficient of dielectric constant (tΕ = –664p pm/°C) combined with a dielectric constant above 110 and a low dielectric loss (tanδ–0.0005 to 0.0006 at 1 MHz) resulted in the nonstoichiometric dielectric ceramics with nominal compositions Ba4Nd2Ti4+xTa6-xO30?x/2 (x = 0.8–1.2).