Very High Power Ultrasonic Additive Manufacturing (VHP-UAM) system was used to produce aluminum parts from 150 μm thick Al3003-H18 foils. The build was processed at 36 μm vibration amplitude, 8 kN normal load, and 3...
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Very High Power Ultrasonic Additive Manufacturing (VHP-UAM) system was used to produce aluminum parts from 150 μm thick Al3003-H18 foils. The build was processed at 36 μm vibration amplitude, 8 kN normal load, and 35.6 mm/s weld speed at 20 kHz frequency. Almost 100% linear weld density was achieved. A deformation-interaction volume of 20 μm was observed below the bonded interface. The microstructural stability including grain boundary structures, and crystallographic orientations was evaluated after annealing these samples at 343°C for 2 hours and 450°C for 2 hours. After heat treatment, small grains persisted at the interfaces with sluggish grain growth kinetics. In contrast, normal grain growth kinetics was observed in the middle of the foils. Possible mechanisms for such phenomena are discussed.
Magnetic semiconductors are of interest for emerging spintronic applications, such as the integration of electronic information processing with magnetic data storage. We report on a new approach - furnace annealing un...
Magnetic semiconductors are of interest for emerging spintronic applications, such as the integration of electronic information processing with magnetic data storage. We report on a new approach - furnace annealing under controlled ambients – aimed at increasing Mn incorporation and synthesizing new magnetic semiconductors with Tc greater than/around room temperature. These annealing treatments are hypothesized to reduce the effect of Mn interstitials. We have obtained preliminary SQUID magnetometry results which indicate ferromagnetic Curie temperatures of around 130 K in (In,Mn) Sb and 60 K in (In, Mn)P. X-ray diffraction was used to characterize phase homogeneity.
Scanning Kelvin probe microscopy (SKPM) and conductive atomic force microscopy (C-AFM) are used to image surfaces of GaN grown by molecular beam epitaxy (MBE). Numerical simulations are used to assist in the interpret...
Scanning Kelvin probe microscopy (SKPM) and conductive atomic force microscopy (C-AFM) are used to image surfaces of GaN grown by molecular beam epitaxy (MBE). Numerical simulations are used to assist in the interpretation of SKPM images. Detailed analysis of the same area using both techniques allows imaging of surface potential variations arising from the presence of negatively charged dislocations and dislocation-related current leakage paths. Correlations between the charge state of dislocations, conductivity of leakage current paths, and possibly dislocation type can thereby be established. Approximately 25% of the leakage paths appear to be spatially correlated with negatively charged dislocation features. This is approximately the level of correlation expected due to spatial overlap of randomly distributed, distinct features of the size observed, suggesting that the negatively charged dislocations are distinct from those responsible for localized leakage paths found in GaN. The effects of charged dislocation networks on the local potential profile is modeled and discussed.
The unique and unprecedented electroluminescence behavior of the white‐emitting molecule 3‐(1‐(4‐(4‐(2‐(2‐hydroxyphenyl)‐4,5‐diphenyl‐1H‐imidazol‐1‐yl)phenoxy)phenyl)‐4,5‐diphenyl‐1H‐imidazol‐2‐yl)n...
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The unique and unprecedented electroluminescence behavior of the white‐emitting molecule 3‐(1‐(4‐(4‐(2‐(2‐hydroxyphenyl)‐4,5‐diphenyl‐1H‐imidazol‐1‐yl)phenoxy)phenyl)‐4,5‐diphenyl‐1H‐imidazol‐2‐yl)naphthalen‐2‐ol (W1), fluorescence emission from which is controlled by the excited‐state intramolecular proton transfer (ESIPT) is investigated. W1 is composed of covalently linked blue‐ and yellow‐color emitting ESIPT moieties between which energy transfer is entirely frustrated. It is demonstrated that different emission colors (blue, yellow, and white) can be generated from the identical emitter W1 in organic light‐emitting diode (OLED) devices. Charge trapping mechanism is proposed to explain such a unique color‐tuned emission from W1. Finally, the device structure to create a color‐stable, color reproducible, and simple‐structured white organic light‐emitting diode (WOLED) using W1 is investigated. The maximum luminance efficiency, power efficiency, and luminance of the WOLED were 3.10 cd A −1 , 2.20 lm W −1 , 1 092 cd m −2 , respectively. The WOLED shows white‐light emission with the Commission Internationale de l′Eclairage (CIE) chromaticity coordinates (0.343, 0.291) at a current level of 10 mA cm −2 . The emission color is high stability, with a change of the CIE chromaticity coordinates as small as (0.028, 0.028) when the current level is varied from 10 to 100 mA cm −2 .
In this paper, an efficient method to characterize the mode II fracture toughness KIIC for materials with preferred interfaces such as wood, fiber composite materials and bonded materials based on the Iosipescu fixtur...
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In this paper, an efficient method to characterize the mode II fracture toughness KIIC for materials with preferred interfaces such as wood, fiber composite materials and bonded materials based on the Iosipescu fixture is developed. A simple formula for calculating KIIC is verified numerically. Our method is easy to implement and is free of friction thereby offering a more reasonable value of KIIC than previous methods. A calibration chart for composite materials is generated. Finite element analysis along with cohesive elements is used to validate experimental load-displacement curves by testing bonded polymers.
An integrated experimental and numerical analysis is carried out to study the interfacial shear strength of bonded materials. Two types of shear tests, namely the losipescu shear test, and the short-beam shear test ar...
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Experiments and complimentary simulations are presented to demonstrate the size-dependent infiltration and detection of variable length nucleic acids in porous silicon with controllable pore diameters in the range of ...
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We describe a fast and efficient method for recognition and quality control of the largearea graphene layers based on image processing algorithms. Results show that our technique is accurate and has potential for indu...
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