Effects of BaO–SiO2 glass particle size on the microstructures and dielectric properties of Mn-doped Ba(Ti,Zr)O3 ceramics

The sintering behavior, microstructures and dielectric properties of Mn-doped Ba(Ti, Zr)O₃ (BTZ) ceramics with different particle sizes of BaO–SiO₂ glass (D50 ranging between 185 and 1200 nm) were investigated. From the metallographic observation, adding finer glass frit revealed more homogeneous compositional distribution. It was found that better spreading of the glass phase could be achieved by adding finer glass particles that could penetrate the BTZ ceramic interface more easily, thus enhancing the grain growth. The extent of the incorporation between glass and ceramic increased with smaller glass particles, and the Curie temperature was altered accordingly. Microstructural evaluation conducted by using X-ray diffraction (XRD) and transmission electron microscopy (TEM) with an energy-dispersive X-ray spectrometer (EDS) indicated the glass particle size has a dramatic influence on the sintering behavior and microstructure of Mn-doped BTZ ceramics. The relationship between microstructures and dielectric properties was also discussed in this study.     

Preparation of poly (hydroxymethyl EDOT)/nano-silver composite films by oxidative polymerization with low-baking temperature,low resistance and good adhesion on PET substrate

Low-resistance films were prepared by polymerization of hydroxymethyl EDOT along with nano-Ag at low-baking temperature (below 120 °C) and low-silver contents (below 20 wt%) on PET substrate. The poly (hydroxymethyl EDOT)/nano-Ag composite films showed low resistance at 21 Ω/□ by spin-coating and at 196 m Ω/□ by drop-casting. We also compared the conductive inks of EDOT, AI4083, nano-Ag and hydroxymethyl EDOT/nano-Ag, and investigated their conductivity, film-forming property and adhesion property. The viscosity of hydroxymethyl EDOT/nano-Ag conductive ink was 12.2 cP at 25.9 °C and suitable for application in flexible plastic devices and inkjet printing technology.     

Nonuniform and Negative Marker Displacements Induced by Current Crowding During Electromigration in Flip-Chip Sn-0.7Cu Solder Joints

A quantitative analysis of the nonuniform distribution of current density and nonuniform rate of electromigration has been carried out by measuring the movement of an array of diffusion markers. Tiny marker arrays were fabricated by focused ion beam on the polished surface of flip-chip solder joints near the anode to measure the electromigration rate. The marker velocity at the current-crowding region was found to be at least five times larger than at locations far from the region. Some of the markers in the low-current-density region possess negative velocities, indicating that backflow occurs during the electromigration. The backflow, in which the atomic flow is against the electron flow, is explained by a constant-volume model as well as the back-stress induced by electromigration.     

The steady state methanol decomposition reaction over Cu/Zn and Cu/Cr catalysts: Pretreatment, operando EXAFS, and activity study

Two commercial Cu catalysts, Cu/Zn and Cu/Cr, were pretreated to produce calcined, partially reduced and completely reduced catalysts, and tested for methanol decomposition. The pretreatments resulted in different initial Cu states based on extended X-ray absorption fine structure (EXAFS) morphological analysis, but only metallic Cu was found after methanol decomposition tests. Pretreatment was found to affect catalytic activity only during the initial transient period, when atom balance analysis showed the presence of excess oxygen in the effluent. The excess oxygen is attributed to the participation of lattice oxygen in the reaction leading to CO₂ and H₂O formation. When there was no excess oxygen present in the effluent, a steady state was achieved and a similar catalytic performance was obtained regardless of catalyst pretreatment conditions.     

Catalyst-free GaN nanorods grown by metalorganic molecular beam epitaxy

High-density GaN nanorods with outstanding crystal quality were grown on c-sapphire substrates by radio-frequency plasma-assisted metalorganic molecular beam epitaxy under catalyst- and template-free growth condition. Morphological and structural characterization of the GaN nanorods was employed by X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy (HRTEM). These results indicate that the rod number density can reach 1/spl times/10/sup 10/ cm/sup -2/ and the nanorods are well-aligned with preferentially oriented in the c-axis direction. Meanwhile, no metallic (Ga) droplet was observed at the end of the rods, which is the intrinsic feature of vapor-liquid-solid method. Nanorods with no traces of any extended defects, as confirmed by TEM, were obtained as well. In addition, optical investigation was carried out by temperature- and power-dependent micro-photoluminescence (/spl mu/-PL). The PL peak energies are red-shifted with increasing excitation power, which is attributed to many-body effects of free carriers under high excitation intensity. The growth mechanism is discussed on the basis of the experimental results. Catalyst-free GaN nanorods presented here might have a high potential for applications in nanoscale photonic devices.     

Development of 1.5‐in. full‐color double‐sided active‐matrix OLED with novel array design

Abstract— A 1.5‐in. full‐color double‐sided AMOLED with a novel array design was fabricated. Different images on both sides of the panel can be controlled by using only one IC driver. High color gamuts of 67% and 81% on the bottom‐ and top‐emitting sides, respectively, were achieved. In addition, good performance on both sides, such as brightness and white balance, were also achieved.     

Radiation simulations of top-emitting organic light-emitting devices with two- and three-microcavity structures

We demonstrate the simulation results of the radiation properties from top-emitting organic light-emitting devices (top-emitting OLEDs) with two- and three-microcavity structures based on the general electromagnetic theory. The parameters of the layer thickness and complex refractive index of each layer, the locations and density of the oscillating dipoles, and the emission photoluminescence spectrum are varied to optimize the device performance. In evaluating the deice performances, the output spectrum, the intensity distribution, and the viewing-angle characteristics of a top-emitting OLED are concerned. The simulation results are consistent with the Fabry-Perot cavity equation, which can be used as a guideline for designing a two-cavity top-emitting OLED. In such a design process, the dipole position is chosen first. Then the thicknesses of the whole organic layer, the semitransparent cathode, and the dielectric layer are adjusted for optimizing the device performance. In a three-cavity top-emitting OLED, not only the emission intensity and the viewing angle can be optimized at the same time, but also the emission wavelength can be independently tuned. Besides, the use of a three-cavity structure helps to narrow the spectral width and increase the color purity.     

Unsteady heat conduction involving phase changes for an irregular bubble/particle entrapped in a solid during freezing – An extension of the heat-balance integral method

Temperature distributions in the molten layer and solid with distinct properties around a bubble or particle entrapped in the solid during unidirectional solidification are determined by applying a heat-balance integral approximation method. The present model can be used to simulate growth, entrapment or departure of a bubble or particle inclusion in solids encountered in manufacturing and materials processing, MEMS, contact melting processes, drilling, etc. In this work, the proposed heat-balance equations are derived by integrating unsteady elliptic heat diffusion equations and introducing the Stefan boundary condition. Due to the time-dependent irregular shapes of phases, coefficients of assumed quadratic temperature profiles are considered to be functions of longitudinal coordinate and time. Temperature coefficients in distinct regions therefore are determined by solving equations governing temperature coefficients derived from heat-balance equations, imposing boundary conditions, and introducing a fictitious boundary condition. The computed temperature fields show agreement with predictions from the finite-difference method. Since the number of independent variables is reduced by one, this work provides an effective method to solve unsteady elliptic diffusion problems experiencing solid–liquid phase changes in irregular shapes.     

Reconstruction design of the lost seismoscope of ancient China

A reconstruction design approach for the lost Zhang Heng’s seismoscope, which was invented in ancient China in 132 AD, is proposed. Based on the literature review, the design requirements of Zhang Heng’s seismoscope are defined and concluded. Then, according to the concepts of generalization and specialization subject to the concluded design requirements, all feasible designs that are in accordance with the science theories and techniques of the subject time period are recreated. Two examples, one with five members and six joints and the other with six members and eight joints, of the interior mechanism of Zhang Heng’s seismoscope are derived with 8 and 26 solutions, respectively. And, this provides a logical foundation for generating all possible reconstruction designs of Zhang Heng’s seismoscope before new evidences are found.     

Efficient energy-saving targets for APEC economies

Energy-saving target ratios (ESTR) for 17 APEC economies during 1991–2000 are computed in a total-factor framework. All nominal variables are transformed into real variables by the purchasing power parity (PPP) at the 1995 price level. The data envelopment analysis (DEA) approach is used to find the energy-saving target (EST) for APEC economies without reducing their maximum potential gross domestic productions (GDPs) in each year. Energy, labor, and capital are the three inputs, while GDP is the single output. Our major findings are as follows: (1) China has the largest EST up to almost half of its current usage. (2) Hong Kong, the Philippines, and the United States have the highest energy efficiency. (3) The energy efficiency generally increases for APEC economies except for Canada and New Zealand. (4) Chile, Mexico, and Taiwan have significantly improved their energy efficiency in the last 5 years. (5) An inverted U-shape relation exists between per capita EST and per capita GDP. (6) ESTR has a positive relation with the value-added percentage of GDP of the industry sector and a negative relation with that of the service sector.