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The hot deformation behavior of a typical nickel-based superalloy was investigated by isothermal compression tests in the temperature range of 1010∼1160 °C and strain rate range of 0.001∼1 s−1. The results indicate that the work hardening, dynamic recovery (DRV) and dynamic recrystallization (DRX) occurred in the alloy during hot deformation. Considering the coupled effects of deformation parameters on the flow behaviors of the alloy, the constitutive models were established to predict the flow stresses during the work hardening-DRV period and DRX periods. In the DRX period, the modified DRX kinetic equation was used to develop the constitutive models, and the strain for maximum softening rate was used in this equation. Additionally, the material constants in the constitutive models were expressed as the functions of Zener-Hollomon parameter by using a linear fitting method. Meanwhile, comparisons between the measured and the predicted flow stresses were carried out, while the correlation coefficient (R) and average absolute relative error (AARE) between the measured and predicted values were also calculated. The results confirm that the developed models could give an accurate estimation of the flow stresses.

Extracting value-added chemicals from renewable resources has attracted much attention in facing the crises arising from fossil resources. This study elucidates a promising strategy of producing valuable organic acids, including maleic acid, formic acid and succinic acid, via a new ozonation process. 5-hydroxymethylfurfural (HMF) and furfural, two platform chemicals obtained from biomass hydrolysis, are used as the raw materials. Under alkaline reaction condition (25 °C, 10 mg/L O3, and 90 min), improved yields of maleic acid, succinic acid and formic acid reached 25.3 wt%, 10.0 wt% and 41.1 wt% from HMF, as well as 17.6 wt%, 2.5 wt% and 79.5 wt% from furfural; respectively. This sustainable manufacturing technology exhibited significant advantages, including one simple process, room condition, avoiding of organic solvent and absence of metal catalysts. This work paves the ways from biomass to commercial organic acids via hydrolysis followed by ozonation.

The hydriding-dehydriding process was used to recycle AZ40 magnesium (Mg) alloy scraps, and the microstructure nanocrystallization was realized. X-ray diffraction analysis, scanning electron microscopy, and transmission electron microscopy were carried out to characterize the microstructure. After mechanically milling in hydrogen for 72 h, matrix Mg was completely turned into nanocrystalline MgH2, with an average crystallite size of about 10 nm. And then, the MgH2 phase was completely transformed into Mg again through vacuum dehydriding treatment at 300 °C for 192 min, with an average crystallite size of about 20 nm. In addition, the nanocrystalline alloy powders were hot-pressed and extruded into bars. The average grain size of the bars was about 500 nm, which had reached the size of ultrafine-grain. Meanwhile, the yield strength and ultimate tensile strength of the as-extruded bars reached about 312 and 497 MPa, respectively. The results indicate that hydriding-dehydriding process is a feasible method for recycling of Mg alloy scraps, and it is expected to have a good application prospect in preparing ultrafine-grain Mg alloys.

Atomic layer deposition (ALD) is potentially a very suitable deposition technology to grow ultra thin films with excellent thickness control, good conformity on high aspect ratio structures, and less defects. Al2O3 and HfO2 are well-established high-k materials to replace SiO2 in transistor and capacitor applications. To grow high quality ALD films with low leakage current, high breakdown electric field and dielectric constant, it is important to understand the impact of both plasma enhanced ALD (PEALD) with O2-plasma and thermal ALD with H2O on the interface between ALD film and substrate surface, and also the impact of the interface on the quality of ALD films. We present the electrical and chemical characterizations of Al2O3 and HfO2 films directly grown on Au, Ti and TiN surfaces. Metal Insulator Metal (MIM) capacitors with 10nm of Al2O3 or 10nm of HfO2 as a dielectric layer were realized.

In this paper, a virtual dynamic model using ADAMS, considering the effects of the mesh stiffness, mesh damping, load inertia, drive ratio and gear backlash is presented for a space manipulator joint. A kind of virtual sweep method is adopted to analyze the resonant frequency of the joint quantitatively and mesh stiffness and load inertia are proposed the key influence factors of frequency property of the joint. In order to design, validate and improve the performance of the joint mechatronic system, the ADAMS and SIMULINK co-simulation is used to build a servo-control model of the joint. The joint motor is derived and modeled, and the dynamic model of the space manipulator joint with sensors and actuator implemented in ADAMS is embedded into SIMULINK environment directly. The speed and position two-loop control system is modeled in SIMULINK, and the control parameters were obtained. A prototype joint and controller are manufactured, a virtual prototype model tuning is implemented through the experimental data. So the co-simulation joint model can be used for the design, simulation and testing of the space manipulator joint.

Silicon nanowires have been patterned with mean widths down to 4 nm using top-down lithography and dry etching. Performance-limiting scattering processes have been measured directly which provide new insight into the electronic conduction mechanisms within the nanowires. Results demonstrate a transition from 3-dimensional (3D) to 2D and then 1D as the nanowire mean widths are reduced from 12 to 4 nm. The importance of high quality surface passivation is demonstrated by a lack of significant donor deactivation, resulting in neutral impurity scattering ultimately limiting the electronic performance. The results indicate the important parameters requiring optimization when fabricating nanowires with atomic dimensions.

A new high-performance normally-off gallium nitride (GaN)-based metal-oxide-semiconductor high electron mobility transistor that employs an ultrathin subcritical 3 nm thick aluminium gallium nitride (Al0.25Ga0.75N) barrier layer and relies on an induced two-dimensional electron gas for operation is presented. Single finger devices were fabricated using 10 and 20 nm plasma-enhanced chemical vapor-deposited silicon dioxide (SiO2) as the gate dielectric. They demonstrated threshold voltages (Vth) of 3 and 2 V, and very high maximum drain currents (IDSmax) of over 450 and 650 mA/mm, at a gate voltage (VGS) of 6 V, respectively. The proposed device is seen as a building block for future power electronic devices, specifically as the driven device in the cascode configuration that employs GaN-based enhancement-mode and depletion-mode devices.

The present projects aims to characterise the performance of an optical test equipment system. The existing system consists of a c-band tuneable laser and an optical spectrum analyser, which are automated by a computer through LabVIEW software. The test system is analysed in terms of accuracy and precision and a dynamic calibration is explored to improve the performance of the system. Specifications are discussed and recommendations are made on how to improve the device test procedure with the available equipment. Finally several optical devices manufactured in the James Watt Nanofabrication Centre are tested within the analysed system. The stopband and its variability according to different injected currents are characterised in terms of reflectivity, where finally the calibration is applied to achieve more precise results. Matlab code is implemented for users of the system. ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- El presente proyecto tiene como objetivo caracterizar el rendimiento de un sistema de prueba de equipos ópticos. El sistema existente se compone de un láser sintonizable de banda C y un analizador de espectro óptico, que están automatizadas por un ordenador a través del software LabVIEW. El sistema de ensayo se analiza en términos de exactitud y precisión y se explora una calibración dinámica para mejorar el rendimiento del sistema. Se discuten las especificaciones y se hacen recomendaciones sobre cómo mejorar el procedimiento de prueba de dispositivos con el equipo disponible. Finalmente varios dispositivos ópticos fabricados en el James Watt Nanofabrication Centre se prueban dentro del sistema analizado. La banda de rechazo y su variabilidad de acuerdo a diferentes corrientes inyectadas se caracterizan en términos de reflectividad, donde finalmente se aplica la calibración para obtener resultados más precisos. Se implementa código Matlab para los usuarios del sistema. Ingeniería Técnica en Electricidad