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Millimeter-wave sintering of ceramic laser host materials has been under investigation at the Naval Research Laboratory (NRL) for high-energy laser (HEL) applications. Potential advantages of polycrystalline, compared to single-crystal, laser host materials include lower processing temperature, higher gain from higher dopant concentration, cheaper fabrication, and larger devices. Successful production...
In this paper, the effect of the stand-off height (SOH) on the microstructure and tensile strength of Cu/Sn-8Zn-3Bi/Cu and Cu/Sn-9Zn/Cu solder joints with SOH of 100 mum, 50 mum, 20 mum and 10 mum were studied. The results show that as the SOH is reduced, the needle-like Zn-rich phase steadily decrease until completely disappeared in both of the two solder joints. For Cu/Sn-9Zn/Cu, Cu5Zn8 IMC is formed,...
Isothermal aging effects on lead-free solders have been extensively investigated in recent studies. There is researches show that aging effects will significantly degrade the mechanical properties of lead-free solders. However, very little work been done on the study of aging effects on the board level dynamic performance of lead-free solder joints, especially for large flip-chip BGA packages for...
In order to enhance thermal conductivity of underfill materials, hexagonal boron nitride (h-BN) was employed as a thermally conductive filler. The relationship between the filler morphology and its effects on the thermal conductivity is focused in this study. Two different h-BN fillers with different morphologies were applied to generate an efficient thermal transport path through the filler and epoxy...
A circumferentially multi-pass butt-welded P91 steel pipe, typically used for high-temperature applications in power plants, has been numerically analysed to determine residual stresses, induced by the process of welding, as well as microstructural regions in the weld, caused by thermal cycles. The finite element (FE) method has been applied to simulate residual stresses generated in the weld region...
Object-oriented finite element analysis (OOF) has recently been shown as an effective tool for evaluating thermo-mechanical material behaviour, because of its capability to incorporate the inherent material microstructure as an input to the model. The complexity of a thermal sprayed microstructure makes it difficult to model and simulate by classical analytical or numerical techniques and thus very...
The effect of temperature and heating rate on density, pore size, porosity, bending strength and water flux of sintered Al2O3 body was studied in this research. Carboxymethyl Cellulose (CMC) 3% by Al2O3 weight was used as additive. The Al2O3 particle sizes were varied at Al2O3 5 mum and the mixture of Al2O3 0.7 mum (50 wt%) and Al2O3 5 mum (50 wt%). The mixture was then extruded, dried and sintered...
Novel approach to improve light extraction efficiency of InGaN-based light emitting diodes with polydimethylsiloxane concave microstructures arrays was demonstrated, which leads to enhancement of extraction efficiency by 1.60-times in good agreement with simulation.
SiC-nanoparticle-mixed Sn58Bi solders were successfully produced by electroplating and the mechanical and microstructural properties of Sn58Bi+SiC solders were observed and analyzed in this study. Dispersed SiC nanoparticles by ultrasonic horn were added into Sn-Bi plating solution. With the SiC added Sn-Bi plating solution, solder bumps were electroplated. After electroplating, the solder bump specimens...
Scandia (Sc)-doped pressed cathodes were prepared by different methods, including mixing of scandium oxide and barium-calcium aluminates with tungsten by manual mechanical mixing, high-energy ball-milling, and liquid-liquid doping. The surface behavior of the active substance, microstructure, and emission properties of the cathodes has been studied by auger electron spectroscopy, scanning electron...
This paper presents a new low-cost, CMOS-compatible and robust wafer-level encapsulation technique developed using a stress-optimised PECVD SiC as the capping and sealing material, imparting harsh environment capability. This technique has been applied for the fabrication and encapsulation of a wide variety of surface- and thin-SOI microstructures that included microcavities, RF switches and various...
In this paper, we describe a modification of the classical hot embossing process which is capable of producing holes in polymer substrates. Substrates with holes that penetrate the complete height of the substrate have been a technical challenge since the first description of the hot embossing process. However most components as, e. g., microfluidic components targeted for biomedical applications...
Reliability of microfluidic designs is an extremely important issue that defines the range of applicability of micro-devices. The reliability design of micro-channels presents new complications that require extensions of today's method to incorporate reliable prediction methodologies. In this paper, using the improved direct simulation Monte Carlo, a prediction method was proposed for the reliability...
This paper describes an integration method of bridging-structural single-walled carbon nanotubes (SWNTs) onto the flexible PDMS sheet by stamping transfer. Silicon microstructures and the SWNTs which directly synthesized between the gaps of the microstructures were lifted off by PDMS stamp sheets with high yield (97.8%) and accuracy (position error <100 nm). From the SEM observation of our transferred...
In this study, the effects of preparation process on the properties of lead magnesium niobate (PMN) based electrostictive materials, such as phase structure, microstructure and electrical property, are investigated and discussed. The results of experiment show the powder samples, fabricated by a modified two-step synthesis method with alkaline-earth metal dopants introduced in the preparation of common...
In this study, Sn-0.7Cu solder alloy was reinforced with Al2O3 (50 nm) and ZrO2 (45 nm) nano particulates to form Sn-0.7Cu/Al2O3 and Sn-0.7Cu/ZrO2 composites. The volume percentge of the Al2O3 and ZrO2 nanoparticulate reinforcement was kept at 1.5%. The composites were synthesized using powder metallurgy technique assisted with microwave sintering and incorporating hot extrusion as secondary processing...
Ferromagnetic Co0.5Cu0.5Fe2O4 and ferroelectric Ba0.8Sr0.2TiO3 composite ceramics, xCo0.5Cu0.5Fe2O4 + (1-x)Ba0.8Sr0.2TiO3 for x = 0.15, 0.3 and 0.45, were prepared by a conventional solid-state reaction method. The crystalline phases of the sintered samples were studied by the X-ray diffraction technique. Scanning electron microscopy (SEM) micrographs were taken to understand the microstructure of...
A porous aluminium plate with a regular columnar microstructure exhibits unusual properties when interacting with high frequency acoustic waves. Finite element modeling reproduces this behaviour and a more detailed analysis explains the underlying physics.
Truxene-oligofluorene nanostructured blends have been controllably patterned with feature size to below 6 mum using inkjet printing and laser direct-writing. Our blending approach provides an attractive method of handling fluorescent macromolecules for optoelectronic applications.
Ultrasonic evaluation of bone has been based on the classical linear elastic theory. However, this theory cannot adequately describe bone's mechanical behavior since the microstructure is neglected. In this study, we use the simplest form of gradient theory (Mindlin FormII) to theoretically derive the velocity dispersion curves for free isotropic bone-mimicking plates and we investigate whether that...
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