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Understanding how the b-wave of the electroretinogram (ERG) is generated by full-field light stimulation is still a challenge in visual neuroscience. To understand more about the origin of the b-wave, we studied the contributions of gap junctions to the ERG b-wave. Many types of retinal neurons are connected to similar and different neighboring neurons through gap junctions. The photopic (cone-dominated) ERG, stimulated by a small light beam, was recorded from goldfish (Carassius auratus) using a corneal electrode. Data were obtained before and after intravitreal injection of agents into the eye under a photopic illumination level. Several agents were used to affect gap junctions, such as dopamine D1 and D2 receptor agonists and antagonists, a nitric oxide (NO) donor, a nitric oxide synthase (NOS) inhibitor, the gap junction blocker meclofenamic acid (MFA), and mixtures of these agents. The ERG b-waves, which were enhanced by MFA, sodium nitroprusside (SNP), SKF 38393, and sulpiride, remained following application of a further injection of a mixture with MFA. The ERG b-waves decreased following N G -nitro-L-arginine methyl ester (L-NAME), SCH 23390, and quinpirole administration but were enhanced by further injection of a mixture with MFA. These results indicate that gap junction activity influences b-waves of the ERG related to NO and dopamine actions.

When the process of planning and production of Pororo is to be analyzed, scientific and meticulous contents planning which considered even cultural discount, and collaborative business partnership which maximized the strength of each participants are found to be the main success factors. Owing to them, Pororo has resulted in continuous profit making through various outlets, the production of series up to 4 seasons, and successful sales in foreign markets. However, OSMU strategy as the key business strategy was not intended from the stage of planning, but was resulted as the business process after good contents were created. In order to have more successful cases like Pororo, and to build a good animation industry ecosystem, efforts by the industry and effective supporting system by the governments should be met.

A 250-nm-thick Al2O3 film was deposited on a Si(100) by a radio-frequency magnetron sputtering and annealed at 1100 °C for various periods of time in air. In the matrix composed of fine metastable-Al2O3 grains of 50–100 nm in diameter, large α-Al2O3 grains of about 2–10 μm in diameter appeared, interestingly aligning themselves along various directions. The compressive stress developed in the alumina films because the thermal expansion coefficient of the film was higher than that of the silicon substrate. The stress distribution in the film is expected to be inhomogeneous due to some discontinuities or defects, such as arrays of dislocation pits and steps on the surface of the Si substrate, which could be generated by intersections of the substrate surface and the slip and twin planes in the Si substrate. The enhanced phase transformation into α-Al2O3 along various directions is suggested to arise from such discontinuities or defects.

The equilibrium shape of pure nickel and the effect of carbon on changes in the equilibrium shape at 1200°C were investigated. A statistical observation on the size-dependent, time-dependent and carbon-induced morphological evolution of crystallites suggested that the equilibrium crystal shape (ECS) of pure nickel is a polyhedron consisting of {111}, {100}, {110} and {210} surfaces. However, crystals with an extensive proportion of {320} surfaces were also frequently observed. The appearance of {320} surfaces was interpreted as kinetically stabilized metastable surfaces, which survived during the thermal equilibrating process, possibly due to a high nucleation energy barrier for their removal. On the other hand, the ECS of pure nickel was observed to change dramatically into a spherical shape with facets of {111}, {100}, {110} and {210} without exception under a carburized atmosphere, which indicates that carbon not only facilitates surface diffusion by which energetically more stable surfaces can be easi...

Dependence of the electrical properties on grain-boundary plane orientation is examined by a combination of high-resolution transmission electron microscopy, impedance spectroscopy, and electron energy-loss spectrometry using two kinds of SrTiO3 Σ5 ([1 0 0]/36.8°) bicrystalline grain boundaries: symmetric (3 1 0) (18.4°/18.4°) and asymmetric (8.4°/28.4°). While the symmetric grain boundary is observed to be straight with the symmetric (3 1 0)//(3 1 0) plane orientation, the asymmetric grain boundary is faceted into symmetric (3 1 0)//(3 1 0) and (2 1 0)//(2 1 0), and asymmetric (1 0 0)//(4 3 0). Grain-boundary impedance is observed only in the asymmetric grain boundary, and the electron energy-loss spectrometry quantification indicates that the asymmetric (1 0 0)//(4 3 0) facets are more oxygen-deficient than the symmetric ones. The results suggest that the asymmetric (1 0 0)//(4 3 0) facets are the most resistive among the three different facets.

The spatially-resolved local impedance can be measured by ‘Millicontact Impedance Spectroscopy (MIS)’, which involves the use of an array of sub-millimeter-scale electrodes. In stabilized zirconia and gadolinia-doped ceria electrolytes with highly resistive grain-boundaries, MIS could measure the local impedance precisely and revealed the spatially-resolved changes in the grain-interior and grain-boundary resistivity. The validity of this technique was illustrated using the examples such as the design of a new scavenger material and an analysis of the diffusion of the siliceous phase along the grain boundary.

This study examines the effect of calcium oxide (CaO) addition to Ce 0.9 Gd 0.1 O 1.95 (gadolinia-doped ceria, GDC) containing 500 ppm SiO 2 on grain-interior and grain-boundary conduction. The GDC can be used as a solid electrolyte for intermediate and low-temperature solid oxide fuel cells. Doping with ≥2 mol% CaO results in a decrease in apparent grain-boundary resistivity at 300 °C from 746.7 kΩ cm to 2.8–3.5 kΩ cm. The total resistivity exhibits a minimum at 2 mol% CaO. Further increase in CaO concentration to 10 mol% results in an increase in grain-interior resistivity from 3.1 to 40 kΩ cm. Although most of the CaO is incorporated into the GDC lattice, a small amount of CaO scavenges the intergranular siliceous phase, which leads to a significant increase in grain-boundary conduction. The increase in grain-interior resistivity at high CaO concentration is attributed to defect association between V O and Ca Ce ″.

This study examined the growth mechanism of In(OH)3 nanocubes formed during the hydrothermal reaction of a solution containing In(NO3)3·6H2O, NaOH, and H2O2. Regardless of the pH of the stock solution, an abnormal growth behavior was detected i.e. only a few particles grew to a very large size. However, the mean edge lengths of the nanocubes decreased significantly from 100–450 to 20–70 nm with increasing pH of the stock solution from 4 to 8.8. This was attributed to the active nucleation of In(OH)3 nanocubes at pH 8.8 and the limitation of their growth due to the restricted source materials. The growth of In(OH)3 nanocubes was explained in terms of a two-dimensional nucleation and growth mechanism.

Crack-free, lead zirconate titanate (PZT) films with a thickness range of 20–100 µm were deposited on silicon substrate by aerosol deposition (AD) process using powders containing 1–12 wt % of organic species prepared by sol–gel route. The as-deposited films were annealed at 700 °C for 5 min by rapid thermal annealing (RTA) to improve the electrical properties. No delaminations or cracks were observed in the annealed film, even for a 100-µm-thick film. The organic species was evaporated during the post-annealing process and generated nano-sized pores which seemed to alleviate the residual compressive stress. Furthermore, a high deposition rate of about 3.3 µm/s was achieved on the film area of 5 ×12 mm2 due to the incorporation of organic residue. The dielectric constant (er), remnant polarization (Pr), and piezoelectric coefficient (d33) of the 20-µm-thick PZT film were 850, 24.0 µC/cm2, and 70 pC/N, respectively, after annealing at 700 °C for 5 min.

The concept of u-Vehicle is a technological model that people try to build the ubiquitous world in the car which moves, by using the RFID technology as well as the telematics service based on the location. RFID is weak on the point of information security because RFID has possibility for being abused such as chasing, counterfeiting, and invading personal privacy. RFID`s tags use a weak cryptographic algorithm. This paper presents the vulnerabilities of information security under u-Vehicle environments. To solve that, we propose a mechanism enhancing RFID tag`s security but with low cost by reducing the number of mutual authentication stages and using the hash function.

The microstructural evolution and dielectric properties of CaCu 3− x Ti 4 O 12− x (3 − x = 2.8–3.05) ceramics were investigated. Normal grain growth behavior was observed at Cu/Ca ≤ 2.9, while abnormal grain growth was observed at Cu/Ca ≥ 2.95. A CuO-rich intergranular liquid phase at Cu/Ca ≥ 2.95 and angular grain morphology were the main reasons for abnormal grain growth. However, the abundant intergranular liquid at Cu/Ca = 3.05 significantly affected the relative dielectric permittivity and dielectric loss. The CuO composition is the key parameter that determines the microstructure and dielectric properties of CCTO ceramics.

The effects of the Zr/Ti ratio on the electrical properties of lead zirconate titanate (PZT) thick films prepared by the aerosol deposition (AD) process were investigated to optimize the electrical properties of the thick film. The Zr/Ti ratio was varied among 45/55, 52/48, and 60/40, and the post-annealing temperature was varied from 500 to 900 °C. Microscopic examination of the as-deposited films revealed crack-free and dense microstructures with a thickness of 10 μm. The annealed films showed markedly improved electrical properties in comparison with the as-deposited films with increasing post-annealing temperature. With increasing Zr/Ti ratio, the remnant polarization and coercive field decreased. The dielectric constant and piezoelectric coefficient, d33, were highest for the PZT 52/48 film. This film annealed at 900 °C exhibited the best overall combination of electrical properties, with a dielectric constant, remnant polarization, and piezoelectric coefficient of 1320, 31.1 μC/cm2, and 150 pC/N, respectively.

Both the presence and absence of an amorphous intergranular film (IGF) between the SiC grains have previously been reported in liquid-phase-sintered SiC ceramics (LPS-SiC). The dominant factor(s) responsible for the grain boundary structure in LPS-SiC has not been clearly revealed. In the present study, LPS-SiC ceramics containing different compositions of sintering additives were fabricated and characterized with respect to their grain boundary structure, using both scanning and transmission electron microscopy. The results suggest that the sintering additive composition plays a dominant role in the evolution of grain boundary structure in LPS-SiC.

This paper proposes MgO as a new scavenger material that can mitigate the harmful effects Of SiO2 impurity on the grain-boundary conduction in 10 mol.% gadolinia-doped ceria (GDC). The addition of 0.3-10 mol.% of MgO resulted in an up to similar to 45-fold increase in the grain-boundary conduction of a GDC specimen containing 500 ppm Of SiO2 impurity. The solubility limit of MgO in GDC was found to be as low as similar to 0.1 mol.% and most of the MgO existed as a second phase. Electron energy-loss spectroscopic analysis indicated the formation of forsterite (MgSiO4), due to a reaction between MgO and the siliceous intergranular phase, to be the scavenging mechanism. (c) 2007 Acta Materialia, Inc. Published by Elsevier Ltd. All rights reserved.

Pure and Nb-substituted CaCu3Ti4−xNbxO12+x/2 (CCTO, x=0, 0.02, 0.1, 0.2, 0.4) ceramics were prepared by a conventional solid-state sintering, and their electric and dielectric properties were investigated using an impedance analyzer. A single-phase CCTO was obtained up to x=0.2 Nb substitution and the lattice parameter increased with Nb substitution concentration. While the grain size decreased with Nb substitution, the resistivity of the grain boundary decreased. The dielectric constant increased with Nb substitution, and the highest value of ∼420 000 was observed in the x=0.2 Nb-substituted specimen at 10 kHz. The obtained electric and dielectric properties in Nb-substituted CCTO were discussed in terms of the internal barrier layer capacitor model, particularly focusing on a ratio of thickness of the grain boundary region to grain size.

With the development of nanotechnology, more attention and care should be paid to grain-boundary structure and its structural transition in order to understand the behavior of polycrystalline materials with grain sizes down to nanometer levels. Here, we report direct evidence suggesting a correlation between a grain-boundary structural transition and a change in the electrical property, using a strontium titanate (SrTiO3) bicrystalline grain boundary as a model system. The electrical properties of grain boundaries in SrTiO3 play a critical role in barrier-layer devices, such as capacitors and varistors. [1] It is believed that the electrical behavior depends on the double Schottky barrier established by the interface charge and the associated space charge across the grain boundary. [2–4] The interface charge arises from the segregation of point defects, which form because the energies to move anions and cations to the grain boundary are different. [5] The consequent electrostatic potential obstructs the transport of charge carriers across the grain boundary. For pure, undoped SrTiO3, Kim et al., [6] using electron energy loss spectrometry (EELS), showed that the ratio of Ti to O concentration in various boundaries is higher than in the bulk, indicating that the grain boundaries are enriched in Ti or deficient in O. Browning et al. [7] reported that a ∑5 grain boundary (∑ denotes the reciprocal of the fraction of common lattice points of the adjoining grains) is segregated by oxygen vacancies. Klie and Browning [8] reported the segregation of oxygen vacancies at a

The abnormal grain growth (AGG) behavior of undoped and SiO 2 -doped CaCu 3 Ti 4 O 2 (CCTO) ceramics were investigated. With the addition of 2wt.% SiO 2 , the AGG-triggering temperature decreased from 1100 to 1060°C, and the temperature for obtaining a uniform and coarse microstructure decreased from 1140 to 1100°C. The lowering of the AGG temperature by SiO 2 addition was attributed to the formation of a CuO-SiO 2 -rich intergranular phase at lower temperature. The apparent dielectric permittivity of coarse SiO 2 -doped CCTO ceramics was ∼10 times higher than that of fine SiO 2 -doped CCTO ceramics at the frequency of 10 3 -10 5 Hz. The doping of SiO 2 to CCTO ceramics provides an efficient route of improving the dielectric properties via grain coarsening. The correlation between the microstructure and apparent permittivity suggests the presence of a barrier layer near the grain boundary.

This study examined the effect of spark plasma sintering (SPS) on the densification behavior and resulting dielectric and piezoelectric properties of Pb(Mg1/3Nb2/3)O3–35 mol% PbTiO3 ceramics with a 5 mol% excess of PbO. Through normal sintering at 1200∘C, the density of the specimen reached only 92% of the theoretical density (TD). However, with the SPS treatment, the density of the PMN-PT ceramics increased to more than 99% of the TD at 900∘C, and maintained over 98% of the TD during subsequent heat-treatment at 1200∘C for 10 h. The increased density of the Pb(Mg1/3Nb2/3)O3–35 mol% PbTiO3 ceramics resulted in an improvement in the dielectric and piezoelectric properties. The SPS treatment was also successfully applied to the densification of a PMN-PT single crystal grown on a BaTiO3 seed crystal using a solid-state crystal growth (SSCG) process.

The equilibrium or growth shape of ceramic materials is classified largely into two categories according to the thermodynamic conditions imposed. One is a polyhedral shape where the surface free energy is anisotropic, and the other a spherical shape where the surface free energy is isotropic. In the case of grains with a polyhedral shape of anisotropic surface free energy, so-called abnormal grain growth usually takes place due to a significant energy barrier for a growth unit to be attached to the crystal surface. In the case of grains with a spherical shape of isotropic surface free energy, however, normal grain growth with a uniform size distribution takes place. In this contribution, the state-of-the-art of our current understanding of the relationship between the crystal shape and the microstructure evolution during the sintering of ceramic materials in the presence of a liquid phase was discussed.

A new approach to improve the grain-boundary conduction in 10 mol% gadolinia-doped ceria (GDC) without any additives was suggested. The grain-boundary conductivity of GDC specimen containing 500 ppm of SiO 2 was increased ∼4 times by post-sintering heat-treatment (HT) at 1350 °C for 20 h. The grain-boundary conductivity showed the maximum at HT temperature of 1350 °C and enhanced with increasing HT time from 0 to 20 h. The mechanism for scavenging resistive siliceous phase by post-sintering HT was investigated with the variation of HT temperatures, HT times, and HT schedules.

The interface atomic structure was proposed to have a critical effect on the microstructure evolution during sintering of ceramic materials. In liquid-phase sintering, spherical grains show the normal grain growth behavior without exception, while angular grains often grow abnormally. The coarsening process of spherical grains with a disordered or rough interface atomic structure is diffusion-controlled, because there is little energy barrier for atomic attachments. On the other hand, kink-generating sources such as screw dislocations or two-dimensional (2-D) nuclei are required for angular grains having an ordered or singular interface structure. Coarsening of angular grains based on 2-D nucleation mechanism could explain the abnormal grain growth behavior. It was also proposed that densification process is closely related to the interface atomic structure. Enhanced densification by carefully chosen additives during solid state sintering was explained in terms of the grain boundary structural transition from an ordered to a disordered open structure.

In a recent work,1 we have reported the optimization of the spark plasma sintering (SPS) parameters to obtain dense nanostructured 3Y-TZP ceramics. Following this, the present work attempts to answer some specific issues: (a) whether ZrO2-based composites with ZrB2 reinforcements can be densified under the optimal SPS conditions for TZP matrix densification (b) whether improved hardness can be obtained in the composites, when 30 vol% ZrB2 is incorporated and (c) whether the toughness can be tailored by varying the ZrO2–matrix stabilization as well as retaining finer ZrO2 grains. In the present contribution, the SPS experiments are carried out at 1200°C for 5 min under vacuum at a heating rate of 600 K/min. The SPS processing route enables retaining of the finer t-ZrO2 grains (100–300 nm) and the ZrO2–ZrB2 composite developed exhibits optimum hardness up to 14 GPa. Careful analysis of the indentation data provides a range of toughness values in the composites (up to 11 MPa·m1/2), based on Y2O3 stabilization in the ZrO2 matrix. The influence of varying yttria content, t-ZrO2 transformability, and microstructure on the properties obtained is discussed. In addition to active contribution from the transformation-toughening mechanism, crack deflection by hard second phase brings about appreciable increment in the toughness of the nanocomposites.

Lead zirconium titanate (PZT) ceramic specimens were prepared by liquid phase sintering with excess PbO. By the addition of a small amount of MgO, the grain shape was changed from spherical to angular. When SiO2 was further added, twin was induced in a few grains, which grew abnormally during heat treatment. Through the electron backscatter diffraction analysis and the observation of three-dimensional grain morphology, the abnormally grown large PZT grains were determined to be penetration twinned. Abnormal grain growth was suggested to be because of reentrant edges formed at the twinned grains.

In an effort to refine the composition and properties of existing hard metals, (W,Ti)C–20 wt% Co cermets have been developed. The present research reports the mechanical and tribological properties of these novel materials. Single-step as well as two-stage and three-stage sintering experiments were conducted on the cermets, processed from the (W,Ti)C solid solution powders. For property comparison, premixed WC/TiC powders were used to fabricate a reference (W,Ti)C–20 wt% Co cermet material. Higher sintered density (9.57 g/cm3) as well as better elastic modulus (467 GPa) and hardness (∼17 GPa) were obtained after three-stage sintering of solid solution powders. In order to evaluate the tribological properties, the fretting wear experiments (mode I, linear relative tangential displacement) were performed against bearing steel for varying normal load in the range of 2–10 N. The experimental results reveal that the steady-state coefficient of friction (COF) varies between 0.50 and 0.65, and a lower COF is recorded at 10 N load for cermets processed from solid solution powders. Under varying tribological conditions, the cermets sintered from solid solution powders exhibit low wear depth (∼1–4 μm) and lower wear rate (7 × 10−7–18 × 10−7 mm3·(N·m)−1 when compared with cermet prepared from the premixed WC/TiC starting powders (wear rate ∼14 × 10−7–22 × 10−7 mm3·(N·m)−1). The wear rate data are critically evaluated based on the phenomenological models. Broadly, abrasive wear is the dominant wear mechanism, and limited contribution from localized spalling of tribolayer and tribochemical wear was also observed.

The energetics and kinetics of carbon nanotube growth are studied using an ab initio method. Specifically, the role of the nitrogen atom is analysed in detail for various pathways to the growth of the nanotube edge. The energy barriers are estimated by identifying transition states and it is found that the growth rate of a zigzag-type edge is significantly enhanced. The underlying physical mechanism is explained based on the electronic structure of nitrogen atoms embedded in the carbon networks.

For the SiC specimens prepared with Al2O3, Y2O3, and CaO (AYC-SiC), it was observed that the intergranular films and triple-junction phases were completely crystallized without subsequent heat-treatment after sintering. The intergranular films were determined to have hetero-epitaxially grown (Al,Si)2OC of a 2H-type wurtzite structure, with partial substitution of Al by Si. Segregation of Ca and Y at the grain boundaries was also detected by energy-dispersive X-ray spectroscopy (EDS). On the other hand, the composition and structure of the triple junction phases were different from those of intergranular films. It showed hexagonal structure and topotactic relationships with SiC grains (aSiC//ajunction, cSiC//cjunction, and aSiC = 2ajunction).

Engineering borides like TiB 2 and ZrB 2 are difficult to sinter materials due to strong covalent bonding, low self-diffusion coefficient and the presence of oxide layer on the powder particles. The present investigation reports the processing of hard, tough and electrically conductive transition metal borides (TiB 2 and ZrB 2 ) based cermets sintered with 6 wt.% Cu using spark plasma sintering (SPS) route. SPS experiments were carried out with a heating rate of 500 K/min in the temperature range of 1200–1500 °C for a varying holding time of 10–15 min and the optimization of the SPS conditions is established. A maximum density of ∼95% ρ th in ZrB 2 /Cu and ∼99% ρ th in TiB 2 /Cu is obtained after SPS processing at 1500 °C for 15 min. While the optimized TiB 2 /Cu cermet exhibits hardness and fracture toughness of ∼17 GPa and ∼11 MPa m 1/2 , respectively, the optimized ZrB 2 /Cu cermet has higher hardness of ∼19 GPa and fracture toughness of ∼7.5 MPa m 1/2 , respectively. High electrical conductivity of ∼0.20 MΩ −1 cm −1 (TiB 2 /Cu) and ∼0.15 MΩ −1 cm −1 (ZrB 2 /Cu) are also measured with the optimally sintered cermets.

The hot-wire silicon chemical vapor deposition (CVD) was approached by the new concept of the theory of charged clusters (TCC). The role of a hot wire is to enhance the rate of negative surface ionization producing negative ions. These ions induce nucleation and produce negatively charged silicon clusters, which deposit as polycrystalline films at low temperatures. During the deposition of silicon, an appreciable amount of negative current (~nA/cm2) was measured, and clusters, a few nanometers in size, were captured and observed by transmission electron microscopy (TEM). The effect of bias on the deposition behavior of the clusters indicated that most of the clusters were negatively charged. In order to deposit films with a large grain size with a high mobility, both the generation of neutral clusters and the cluster size should be minimized. A working pressure of 0.3 Torr and a wire temperature of 1800 °C were found to be optimal. Under these conditions, the film with grain size of almost 1 μm could be deposited with a mobility of 175 cm2/Vsec.

Conductivity profiles of nitrogen-graded zirconia from nitridation of 2 mol% yttria-doped tetragonal zirconia polycrystals (2Y-TZP) were determined using microcontact impedance spectroscopy. Local conductivity variations were interpreted in terms of nitrogen concentration and the morphological distribution of the tetragonal precipitates in the two-phase region of nitrogen partially stabilized zirconia (N-PSZ). Nitrogen incorporation in the stabilized zirconia was found to strongly decrease the local conductivity below 400°C, even though the oxygen vacancy concentration increased nominally. This behavior is ascribed to the strong vacancy–vacancy interaction leading to vacancy ordering. The strong interaction is indicated by the formation of ordered-vacancy phases in nitrogen-doped zirconia. Percolation of elongated tetragonal precipitates of lesser nitrogen concentration and thus of higher conductivity explains the conductivity anisotropy observed by microcontact measurements as well as the large effective dielectric constants.

The effect of dc electric field upon the spatial variation of microstructure during the sintering of BaTiO3 in a N2 atmosphere was investigated. When BaTiO3 specimens were heat-treated in a N2 atmosphere at 1350 ∘C under an electric field, grain growth was enhanced at the positive-biased region for a 0.5 mol% Nb-doped specimen, while it was promoted at the negative-biased region for a 3.0 mol% Nb-doped specimen. The grain growth behavior at both the positive and negative-biased region was similar for a 1.0 mol% Nb-doped specimen. The results have been explained mainly in terms of the boundary potential, which varies with the donor concentration, and the oxygen partial pressure of the surrounding atmosphere.

ZnO ceramics doped with a small amount of Bi 2 O 3 and Sb 2 O 3 were prepared and their orientation-dependent etching patterns were analyzed. Three distinctive patterns produced by the oxidizing etchant HCl were observed: hexagonal etch pits on + C plane, triangular etch pits on prismatic plane, and hillocks of hexagonal pyramid on − C plane. From these results, the three-dimensional shape of etch pit could be suggested. The character of inversion boundary was also determined from the etching patterns.

For a twinned face-centered-cubic crystal, the energy barrier for two-dimensional nucleation on a concave trough (or a re-entrant edge) and that for a layer advancing across a convex ridge were calculated. The former was obtained by analyzing the line tension of the trough. The results show that their energy barriers are 39 and 50% compared to that for nucleation on a flat {111} face, respectively. Therefore, the layer advance across the ridge is found to be more difficult than the nucleation on the trough. Based on these results, the morphology of the growing surface is predicted and an alternative growth process by the twin-plane-re-entrant-edge mechanism is suggested.

Impedance spectroscopy with spatial resolution using a microcontact array has successfully been applied to nitrogen-graded zirconia to establish the conductivity variation with nitrogen dopant concentration. Impedance profiles were measured in two configurations: 1) using one microelectrode versus a large counter electrode and 2) measuring between two microelectrodes. A versatile equivalent circuit model was introduced which allows a straightforward analysis of the obtained spectra which exhibit inductive loops as frequently associated with two-microcontact measurements. The analysis unambiguously revealed a local conductivity anisotropy in the material.

The effect of glassy-phase, using AlN and Lu2O3 as sintering additives, on the microstructure and mechanical properties of liquid-phase-sintered, and subsequently annealed SiC ceramics was investigated. The microstructure was strongly influenced by the sintering additive composition, which determines the intergranular phase (IGP). The average thickness of SiC grains increased with increasing the Lu2O3 /(AlN + Lu2O3) ratio, whereas the average aspect ratio decreased with increasing the molar ratio. The homophase and heterophase boundaries of the SiC ceramics were completely crystalline in all specimens. The room temperature (RT) strength decreased with increasing the molar ratio whereas the RT toughness showed a minimum at the molar ratio of 0.6. The best results at RT were obtained when the molar ratio was 0.2. The flexural strength and fracture toughness of the ceramics were >700 MPa and ~6 MPa.m1/2 at RT. The high temperature strength was critically affected by the chemistry, especially the content of Al in the IGP. The best strength at temperatures ³ 1500oC was obtained when the molar ratio was 0.5. Flexural strengths of the ceramics at 1500oC and 1600oC were 610 ± 80 MPa and 540 ± 30 MPa, respectively. The beneficial effect of the new additive compositions (Lu2O3-AlN) on high-temperature strength of SiC ceramics was attributed to the crystallization or removal of IGP and introduction of Al into SiC, i.e., removal or reduction of Al content from the IGP, resulting in an improved refractoriness of the IGP.

The grain growth behavior of La-doped BaTiO3 specimens was investigated at 1350 °C under DC external electric field. In air atmosphere, grain growth was enhanced at the positive-biased region for the 0.15 mol% La-doped and 0.3 mol% La-doped specimens, while it was enhanced at the negative-biased region for the 1.0 mol% La-doped specimen. For the 0.6 mol% La-doped specimen, on the other hand, both positive- and negative-biased regions showed the same grain size. The demarcation donor composition (0.6 mol% La) shifted to a higher donor concentration when the specimen was heat-treated in nitrogen. The results were explained in terms of the grain boundary potential and its variation with donor concentration, oxygen partial pressure, and defect polarization.

In this study, the microstructure and property of poly-Si film, deposited using hot wire chemical vapor deposition (HWCVD) were investigated. A consequence of the low a-Si content in the poly-Si film was crystallites with well developed facets. The crystallite morphology was rhombic pyramidal while EBSD analysis revealed the existence of (1 1 1) contact twin planes. The facets of the rhombic pyramidal crystallites were based on { 3 2 0 } and { 3 2 0 } * planes, which have Σ 3 twin relationship with respect to (1 1 1) contact twin plane.

Spontaneous generation of charged atoms or clusters was investigated during thermal evaporation of silver. For this, the effect of the applied electric bias on the film growth rate was examined during evaporation of silver at 1373 K in a tungsten basket. Film growth rates on three silicon substrates biased + 300, 0 and −300 V with respect to the chamber were 300, 420 and 960 nm per hour, respectively. The number density of generated positively-charged atoms or clusters could be measured by the electric current on the Faraday cup in the chamber. From the temperature dependence of the positive current, the activation energy for charging was determined to be ∼ 2.2 eV. This value could be best explained by the surface ionization of clusters of a few atoms on the oxidized tungsten surface.

The influence of TiO 2 additives on the sintering behavior of In 2 O 3 ceramics has been investigated. TiO 2 increases the densification rate, decreases the grain growth during the intermediate stage of sintering, and hinders the pore/ boundary breakaway that can affect the final stage of sintering. For a given grain size, TiO 2 shifts the grain size/density trajectory toward higher densities. TiO 2 mainly acts by a second-phase mechanism, but it also may decrease the decomposition rate of In 2 O 3 .

The low-temperature degradation of zirconia (ZrO 2 ) that was doped with 3 mol% yttria (Y 2 O 3 ) (3Y-TZP) was prevented by the heat treatment of sintered specimens in nitrogen. The heat treatment of sintered specimens resulted in a surface layer that was stabilized by nitrogen ions, whereas the interior was only slightly affected by the heat treatment. X-ray diffractometry and transmission electron microscopy analyses revealed that the stabilized surface layer consisted of cubic grains with tetragonal precipitates. Although the presence of the surface layer decreased the strength of the sintered 3Y-TZP, the strength of nitrified specimens was maintained when low-temperature annealing was applied.

For large-grained manganese zinc (MnZn) ferrite ceramics, grain misorientation determined by electron backscatter diffractions and grain-boundary resistance measured using microcontact impedance spectroscopy have been correlated. The degree of oxidation of grain boundaries and, hence, the barrier height depends on the overall grain-boundary network as well as on the individual boundary structure; therefore, a statistical analysis has been performed based on several hundreds of local measurements. When the boundaries are divided into low- and high-resistance groups, statistically significant differences in rotation axis and angle distributions are found. The misorientation distribution of the low-resistance boundary group is suggested to reflect the low-energy configurations of boundary planes in MnZn ferrites.

Sintering of In2O3 has been carried out in air to full density. Because of the difference in densification between the agglomerates and the matrix, large interagglomerate pores were observed to form at the initial stage of sintering. Such pore formation could be prevented by applying a small external pressure which resulted in the beneficial rearrangement of agglomerates.

Microstructural evolution during the heat treatment of cement clinker was investigated. Two model specimens, which consisted of faceted tricalcium silicate (C3S) and spherical dicalcium silicate (C2S) grains dispersed in a liquid matrix, were prepared with 5 wt% of large seed particles. The seed particles of faceted C3S grains grew extensively, whereas those of the spherical C2S grains grew rather slowly, relative to the matrix grains. As a consequence, C3S grains exhibited a bimodal size distribution that was typical of exaggerated grain growth, whereas C2S grains retained a uniform and normal size distribution. These results suggest that the growth of faceted C3S grains was controlled by the interface atomic attachment, such as two-dimensional nucleation, and that of spherical C2S grains was controlled by diffusion through the liquid matrix. The dependence of growth mechanisms on grain morphology has been explained in terms of the atomistic structure of the solid/liquid interface.

Sintered tetragonal-zirconia polycrystals (TZP) were embedded in a zirconium nitride powder bed and heat-treated at various temperatures. Surface layers of the TZP specimens were transformed to a stabilized cubic-zirconia by nitrogen incorporation, and their thickness was observed to increase by a parabolic rate law. The nitrogen diffusivity was evaluated from the temperature dependence of the nitridation rate. The microstructure of the nitrided layer was composed of different zones of equiaxed and columnar grains. The columnar grains were developed along the nitrogen flux lines. The observed microstructural evolution was explained in terms of nucleation and growth kinetics of nitridation.

The effect of an external electric field on the grain-boundary migration in Al2O3 ceramics has been investigated. The boundary migration is dependent on the direction and magnitude of the applied bias, and the observed boundary migration behavior is attributed to the presence of an electrostatic potential that inherently forms at the grain boundaries of Al2O3 ceramics. The results give experimental evidence that the boundary phenomena in oxide ceramics are related to the grain-boundary potential.