Powder and ceramics of barium titanate prepared by the citric process were studied by x-ray photoelectron spectroscopy (XPS). Spectra of C1s, O1s, Ti2p, Ba3d, and Ba4d levels are analyzed in powder and ceramics immediately after the sintering step and after several months of exposure in the air. Ar-ion etching allowed one to characterize the material intrinsic carbon. The results are discussed in comparison with works previously published on oxide single crystals.

The effect of changes in the oxygen partial pressure during the heat treatment of Bi-2223 tapes has been investigated. Distinct differences were observed in the phase assemblages, compositions, and critical current densities. Of particular importance in the correlation of transport properties and microstructure was the redistribution of lead in both the secondary phases and the Bi-2223 matrix. The highest Jc values were associated with tapes that contained Ca2PbO4 as part of the phase assemblage coupled with lower concentrations of lead in the superconducting phase. The high Jc of 30.4 kA/cm2 was obtained in tapes processed at 820 °C where the oxygen partial pressure was increased from 10% O2/Ar to 20% O2/Ar after 25 h of each 50-h sinter cycle. Samples processed only in 10% O2/Ar at 820 °C did not contain Ca2PbO4, had slightly higher concentrations of lead in the superconducting phase, and had significantly lower Jc values.

By adsorption of monosilicic acid on aluminum hydroxide, an amorphous aluminosilicate (AAS) of Si/Al ratio of 1/3 was formed. When the AAS was heated to 1000 °C, mullite (3Al2O3 · 2SiO2) crystallized directly without the formation of a spinel phase. It was clearly evidenced that correct adjustment of three factors, the Si/Al ratio, the proportion of 4- and 6-coordinated aluminums, and the single environment of a unit (no Si–O–Si bond), is important for the direct mullitization from AAS.

Microwave dielectric properties of the solid solution between Ba(Ni1/3Nb2/3)O3 and Ba(Zn1/3Nb2/3)O3 were investigated. Samples were prepared by the conventional mixed oxide method as well as the Pechini method. Sintered samples were analyzed using x-ray diffraction and scanning electron microscopy, and their microwave dielectric properties were measured by the post resonator method. The sample prepared by the Pechini method revealed excellent dielectric properties, i.e., permittivity of 35.6, quality factor of 5700 at 10 GHz, and very small temperature coefficient of resonant frequency. Order-disorder behavior of this solid solution system was found to depend on processing parameters. Variation in microwave dielectric properties was discussed in terms of the order-disorder behavior, chemical composition, mixture rule, etc.

Nanoparticles of Ag, Au, Pd, and Cu have been prepared by the reduction of their salts by ethyl alcohol under refluxing conditions in the presence of polyvinylpyrrolidone (PVP). In the case of Au and Cu, it was necessary to use magnesium metal as a catalyst during the reduction. The nanoparticles are in the 5–35 nm range in the case of Ag, Au, and Pd, but there is considerable agglomeration in the case of Cu even in the presence of PVP.

The nanocrystallization process of the amorphous Fe–Mo–Si–B alloy under ball milling is characterized by means of transmission Mössbauer emission spectroscopy (TMES) in the present paper. It was found that a single α–Fe phase with the bcc structure is formed under ball-milling the amorphous Fe–Mo–Si–B alloy. A significant increase in the relative area of the subspectra of 8Fenn and 7Fenn and a remarkable decrease in isomer shift and half linewidth of the subspectra of various Fe configurations, especially in the case of 6Fenn, were observed during the ball-milling process. The diffusion of metalloid atoms from the bcc α–Fe phase to the remaining amorphous phase and α–Fe/α–Fe grain boundaries is suggested to occur during the mechanical crystallization of the current amorphous alloy based on the above TMES investigations.

Silica composites containing nanometer dimension colloids have been fabricated by implantation of Ag ions followed by Sb ions, and by implantation of Sb ions followed by Ag ions. Doses for the sequential element implantations were in ratios of 9 : 3 Ag : Sb and 3 : 9 Sb : Ag with the total dose held constant at 12 × 1016 ions/cm2. Energies of implantation were 305 keV for the Ag ions and 320 keV for the Sb ions. Single element colloids were also fabricated by implantation of Ag or Sb using the same nominal dose and implantation energy of the sequential implantations. Approximately spherical particles were formed in all implanted samples. Microstructures of the nanoclusters in the various samples were markedly different. Selected area diffraction techniques revealed that alloyed phases of Ag–Sb were formed in some of the sequential implantations. The microstructure and the optical response of the nanocluster glass composites were found to be strongly dependent upon the order of the ion species implanted. The optical spectra of the 3 : 9 Sb : Ag sample displays two resonance peaks indicative of a Ag resonance peak and a resonance peak of an alloyed phase of Ag–Sb. Optical spectra for the 9 : 3 Ag : Sb sample displays two broad absorption peaks indicative of coated particles.

Brazing of aluminum nitride (AlN), which is a good ceramic substrate in high power electronic applications, to copper was investigated using In-base active fillers. Compositions of brazing fillers were chosen as In–1 wt.% Ti (IT1), In–19 wt.% Ag–2 wt.% Ti (IAT2), In–15 wt.% Ti (IT15), and In–52 wt.% Ag–20 wt.% Cu–3 wt.% Ti (ACIT3). Brazing operation was performed in vacuum at temperatures of 650–900 °C. The brazing fillers showed good wetting on AlN and led to a strong bond between AlN and braze alloy. From the microstructural analysis, no evidence of reaction layer was clearly found at the interface under the experimental brazing conditions. The composition of brazing alloy layer changed into Cu9In4 phase due to the extensive dissolving of Cu from base metal. Bond strength, measured by 4-point bend test, was obtained as high as 23–30 kgf for the Cu/AlN/Cu joint brazed with IT15 and ACIT3 fillers, and shown to be nearly constant even when the temperature was varied within 700–800 °C. Most of the fracture appeared to proceed through the interior of the AlN ceramic. Based on the experimental results, it is believed that a strong bonding between AlN and braze alloy can be achieved without the apparent forming of a Ti-rich reaction layer at the interface.

We have investigated reactive phase formation in magnetron sputter-deposited NiyAl multilayer films with a 1 : 3 molar ratio and various periodicities, L, ranging from 320 nm down to a codeposited film with zero effective periodicity. The films were studied by x-ray diffraction, differential scanning calorimetry, electrical resistance measurements, and transmission electron microscopy. We find that Ni and Al have reacted during deposition to form the B2 NiAl phase and an amorphous phase. The formation of these phases substantially reduces the driving force for subsequent reactions and explains why nucleation kinetics become important for these reactions. Depending on the periodicity, these reactions result in the formation of NiAl3 or Ni2Al9 followed by NiAl3. Detailed calorimetric analysis reveals differences in the nucleation and growth behavior of NiAl3 compared with other studies.

A novel approach has been used to develop (100) faceted diamond films with flat, smooth surfaces. A morphological study of the early stages of growth behavior of (100) homoepitaxial films versus process temperature and methane percentage was carried out using atomic force microscopy. The results showed that spiral growth features and penetration twin density were dominant for growth conditions not well suited for (100) growth. Optimized process parameters were found to proceed via a step mechanism consistent with ledge growth on (2 × 1) reconstructed (100) diamond surfaces. These optimized conditions were then applied to growth of polycrystalline diamond on pretreated silicon substrates. A unique octahedral faceted film resulted, indicating strong preference for growth in the 〈100〉 direction. Scanning electron microscopy, x-ray diffraction, and Raman spectroscopy were used to assess film morphology, internal fiber texture, and carbon phase, respectively. A second stage growth step was used to flatten the surface topography to achieve the desired (100) flat tile-like morphology. This smooth (100) surface exhibited enhanced tribological performance compared to a typical randomly textured diamond film.

In this research, a fatigue model for ferroelectric materials is proposed. The reasons for the electrical fatigue resistance of SrBi2Ta2O9 (SBT), SrBi2Nb2O9 (SBN), and PbZr1−xTixTixO3 (PZT) are discussed in terms of the bulk ionic conductivities of the compounds. To obtain the bulk ionic conductivity of SBT and SBN, we have used impedance spectroscopy which provides an effective method that allows us to separate the individual contributions of bulk, grain boundaries, and electrode-ferroelectric interfaces from the total capacitor impedance. The bulk ionic conductivities of SBT and SBN (∼10−7 S/cm) are much higher than those of the perovskite ferroelectrics, e.g., PZT (∼10−11–10−10 S/cm). The high ionic conductivities led us to conclude that the good fatigue resistance of SrBi2Ta2O9 and SrBi2Nb2O9 is due to easy recovery of defects. Specifically, oxygen vacancies entrapped within the capacitors are easily released, resulting in limited space charge buildup and domain wall pinning during the polarization reversal process. However, the oxygen vacancies in PZT are trapped at trap sites to become space charges, resulting in capacitor fatigue.

Chemically homogeneous BaxSr1−xTiO3 (BST with x = 0.6) multicomponent sol was synthesized using barium oxide, strontium chloride, and Ti-alkoxide (titanium isopropoxide) as starting materials. Acetylacetone (AcAc) was introduced as a chelating agent to reduce a rapid hydrolysis rate of Ti-alkoxide. Analysis of Fourier transform infrared spectroscopy (FTIR) spectra indicated that the stabilization of BST sols was achieved by the chelation of Ti-alkoxide with the enolic form of AcAc. The effective activation energy associated with the formation of perovskite phase from the xerogel was estimated by the differential thermal analysis (DTA) experiment using various heating rates. It is approximately 400 kJ/mol with the Avrami exponent (reaction order) of n = 1, suggesting that the growth of perovskite BST is diffusion-controlled. The calculated half-life time suggests that the minimum temperature for the crystallization which is practically accessible to a real processing is approximately 600 °C. The BST thin film fabricated on the “Pt(150 nm)/Ti(100 nm)/SiO2(100 nm)/Si” substrate exhibited the relative dielectric permittivity of 310 and can be represented by an equivalent circuit consisting of a resistive component originated from the bulk perovskite grain and a parallel RC component resulting from the presence of the grain boundary.

The microstructure of NiZr2 in the course of amorphization by ball-milling is studied by transmission electron microscopy (TEM) and x-ray diffraction (XRD). The evolution from the initial fully crystalline alloy to a fully amorphized material is described. It is shown that prior to amorphization, the powder aggregates achieve a 100% nanocrystalline structure; the amorphous phase then appears and develops to the expense of the nanocrystalline phase. No massive chemical disordering is observed, but a small amount cannot be ruled out. It is proposed that amorphization occurs by chemical disordering at interfaces, induced by the scattering of shear waves.

A high-purity, single-phase TiO2 ceramic with high density, strength, and electrical conduction was developed as a key structural material for the production equipment of semiconductors. Green bodies were made of high purity rutile TiO2 of very fine powder. They were sintered in air at 1200 °C for 2 h and then were hot isostatically pressed (HIPed) in argon at 1000 °C, 150 MPa for 2 h. HIPed TiO2 ceramics were found to be electrically conductive and pore free. Their relative density, specific resistance, and bending strength were 100%, 1 Ω ·cm, and 300 MPa, respectively. No strength degradation was found to the temperature up to 1000 °C. This material has high potential for use as electrically conductive structure materials in the semiconductor industry.

Composite powders of molybdenum silicide–SiC were synthesized by reacting mixtures of (Mo–SiO2 –C), (Mo–Si3N4 –C), and (Mo–SiO2 –Si3N4 –C) powders at 1300 °C. In the (Mo–SiO2 –C) system Mo5Si3 and Mo3Si formed predominantly. MoSi2 formed the major constituent of the reaction product from powder mixtures containing Si3N4. Vapor-solid SiC whiskers formed in the (Mo–SiO2 –C) system. Vapor-liquid-solid whiskers of SiC and Mo5Si3C formed in (Mo–SiO2 –Si3N4–C) and (Mo–Si3N4 –C) systems, respectively. The mechanism of formation of the VLS whiskers and molybdenum silicides was identified as follows: initially a thin layer of Mo2C forms on Mo particle; the Si vapor from thermal decomposition of Si3N4 deposits on the Mo2C surface and forms a droplet of ternary “Nowotny phase” Mo<5Si3C<1; an SiC/Mo5Si3C whisker forms by nucleation and growth from the supersaturated ternary phase; after reaction with the Mo2C layer, the SiO/Si vapor further reacts with Mo particle to form bulk silicides.

A method for the preparation of pure amorphous Fe2O3 powder with particle size of 25 nm is reported in this article. Pure amorphous Fe2O3 can be simply synthesized by the sonication of neat Fe(CO)5 or its solution in decalin under an air atmosphere. The Fe2O3 nanoparticles are converted to crystalline Fe3O4 nanoparticles when heated to 420 °C under vacuum or when heated to the same temperature under a nitrogen atmosphere. The crystalline Fe3O4 nanoparticles were characterized by x-ray diffraction and M¨ossbauer spectroscopy. The Fe2O3 amorphous nanoparticles were examined by Transmission Electron Micrography (TEM), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), and Quantum Design SQUID magnetization measurements. The magnetization of pure amorphous Fe2O3 at room temperature is very low (<1.5 emu/g) and it crystallizes at 268 °C.

The chemical reactions between hyperthermal species from a methane plasma and the boron nitride surface have been studied. In this work we report an x-ray photoemission study of the boron nitride with varying degrees of carburization. The carbon ions react, forming C–B and C–N bonds; for surface carbon concentration, smaller than ,∼0.30, C–B bonds are formed, while for higher surface carbon concentrations C–N bonds are also observed. In addition, the binding energy difference between the N1s and B1s core levels increases with increasing carbon content of the film. These chemical shifts are interpreted in terms of the decrease of the ionicity of the material as a consequence of the increase in the number of C–B and C–N bonds. For surface carbon concentration higher than 0.30, amorphous carbon is also formed that grows and finally forms a surface layer. The valence band spectra of the BNC compounds show that the density of states filling the gap at about 15 eV between the two characteristic peaks of the valence band of BN, marking the nitrogen 2s orbitals and the boron and nitrogen 2p electrons and the orbital hybridization between the 2s of boron and 2p states, increases with increasing carbon fluence as a consequence of the hybridization with carbon orbitals.

Microstructure evolution in amorphous Ge/Si multilayers grown by dual-target dc magnetron sputtering was investigated by cross-sectional transmission electron microscopy, x-ray diffraction, and growth simulations. In films grown under low intensity ion-irradiation conditions, the structure is columnar with low-density regions along column boundaries where layer intermixing was observed. By increasing the low-irradiation intensity (controlled by an applied negative substrate-bias), structures with smooth and well-defined layers could be grown. This was achieved at bias voltages between 80 and 140 V, depending on the sputtering gas pressure. As the ion-irradiation intensity is further increased, ion-induced intermixing degrades the layer interfaces and finally an amorphous Si1−xGex alloy forms. The combination of x-ray diffraction measurements and reflectivity calculations reveals an asymmetry between the Ge/Si and Si/Ge interface widths due, primarily, to a corresponding asymmetry in incident particle energies during the growth of alternate layers.

The Weibull modulus is widely used for estimating the reliability of ceramic components in engineering applications. An improvement in the evaluation of the Weibull modulus is achieved by using an appropriate weight function to the data points while fitting a straight line to the Weibull plot by the least square method. The conventional weight function is a function of the probability of failure. This paper describes an alternate method of obtaining the weight function based on first principles. This modified weight function is a function of the stress at failure rather than probability of failure. Evaluation of the two-parameter Weibull modulus was estimated on simulated strength distribution data with both the weight functions. A comparative analysis indicates that the modified weight function gives a different result than the conventional weight function. The paper also highlights the effect and importance of uncertainties in the measurement of strength on the calculated Weibull modulus.

The basic ballistic failure mechanisms and their sequence occurring in dense alumina tiles during projectile penetration were investigated. The alumina tiles were supported by semi-infinite support blocks made of three different materials. Initially, a drop-weight test (DWT) was used to gain an insight into the damage mechanisms and sequence during quasi-static impact conditions. The quasi-static damage mechanisms were compared with the damage obtained in 0.3 cal. armor-piercing tests (APT). The DWT's results suggested the following sequence of quasi-static failure mechanisms: Radial tensile cracks, associated with the low tensile strength of the ceramic formed initially, as a result of the bending induced by local deformation at the opposing surface. Subsequently, a shear-dominated cone crack propagated from the edge of the contact zone. If sufficient energy was available, crushing of the material beneath the contact zone developed during the final stages of failure. It is shown that these so-called “quasi-static” damage mechanisms, identified from the DWT's, also corresponded to the damage mechanisms and sequence during APT's.