On kinematic relaxation and deposition of water droplets in the last stages of low pressure steam turbines

In the first part of the paper steady two-phase flow predictions have been performed for the last stage of a model steam turbine to examine the influence of drag between condensed fog droplets and the continuous vapour phase. In general, droplets due to homogeneous condensation are small and thus kinematic relaxation provides only a minor contribution to the wetness losses. Different droplet size distributions have been investigated to estimate at which size inter-phase friction becomes more important. The second part of the paper deals with the deposition of fog droplets on stator blades. Results from several references are repeated to introduce the two main deposition mechanisms which are inertia and turbulent diffusion. Extensive postprocessing routines have been programmed to calculate droplet deposition due to these effects for a last stage stator blade in three-dimensions. In principle the method to determine droplet deposition by turbulent diffusion equates to that of Yau and Young [1] and the advantages and disadvantages of this relatively simple method are discussed. The investigation includes the influence of different droplet sizes on droplet deposition rates and shows that for small fog droplets turbulent diffusion is the main deposition mechanism. If the droplets size is increased inertial effects become more and more important and for droplets around 1 μm inertial deposition dominates. Assuming realistic droplet sizes the overall deposition equates to about 1% to 3% of the incoming wetness for the investigated guide vane at normal operating conditions. Copyright © 2013 by Solar Turbines Incorporated.

Mn-including InAs quantum dots fabricated by Mn implantation

Mn-including InAs quantum dots (QDs) were fabricated by Mn-ion implantation and subsequent annealing. The optical, compositional, and structural properties of the treated samples were analyzed by photoluminescence (PL) and microscopy. Energy dispersive X-ray (EDX) results indicate that Mn ions diffused from the bulk GaAs into the InAs QDs during annealing, and the diffusion appears to be driven by the strain in the InAs QDs. The temperature dependence of the PL of Mn-including InAs QD samples exhibits QDs PL characteristics. At the same time, the heavy Mn-including InAs QD samples have ferromagnetic properties and high T-c. (c) 2008 Elsevier B.V. All rights reserved.

Formation of total-dose-radiation hardened materials by sequential oxygen and nitrogen implantation and multi-step annealing

Separation by implantation of oxygen and nitrogen (SIMON) silicon-on-insulator (SOI) materials were fabricated by sequential oxygen and nitrogen implantation with annealing after each implantation. Analyses of SIMS, XTEM and HRTEM were performed. The results show that superior buried insulating multi-layers were well formed and the possible mechanism is discussed. The remarkable total-dose irradiation tolerance of SIMON materials was confirmed by few shifts of drain leakage current-gate source voltage (I-V) curves of PMOS transistors fabricated on SIMON materials before and after irradiation.

The formation and stability of Si1-xCx alloys in Si implanted with carbon

Si1-xCx alloys of carbon (C) concentration between 0.6%-1.0% were grown in Si by ion implantation and high temperature annealing. The formation of Si1-xCx alloys under different ion doses and their stability during annealing were studied. If the implanted dose was less than that for amorphizing Si crystals, the implanted C atoms would like to combine with defects produced during implantation and it was difficult to form Si1-xCx alloys after being annealed at 850 degreesC. With the increment of implanted C ion doses, the lattice damage increased and it was easier to form Si1-xCx alloys. But the lattice strain would become saturate and only part of implanted carbon atoms would occupy the substitutional positions to form Si1-xCx alloys as the implanted carbon dose increased to a certain degree. Once Si1-xCx alloys were formed, they were stable at 950 degreesC, but part of their strain would release as the annealing temperature increased to 1 000 degreesC. Stability of the alloys became worse with the increment of carbon concentration in the alloys.

Study on pulsed laser ablation and deposition of ZnO thin films by L-MBE

ZnO, as a wide-band gap semiconductor, has recently become a new research focus in the field of ultraviolet optoelectronic semiconductors. Laser molecular beam epitaxy (L-MBE) is quite useful for the unit cell layer-by-layer epitaxial growth of zinc oxide thin films from the sintered ceramic target. The ZnO ceramic target with high purity was ablated by KrF laser pulses in an ultra high vacuum to deposit ZnO thin film during the process of L-MBE. It is found that the deposition rate of ZnO thin film by L-MBE is much lower than that by conventional pulsed laser deposition (PLD). Based on the experimental phenomena in the ZnO thin film growth process and the thermal-controlling mechanism of the nanosecond (ns) pulsed laser ablation of ZnO ceramic target, the suggested effective ablating time during the pulse duration can explain the very low deposition rate of the ZnO film by L-MBE. The unique dynamic mechanism for growing ZnO thin film is analyzed. Both the high energy of the deposition species and the low growth rate of the film are really beneficial for the L-MBE growth of the ZnO thin film with high crystallinity at low temperature.

Photoluminescence and activation on SI-GaAs by Si+ implantation and following rapid thermal annealing

Photoluminescence (PL) and electrical characteristics of SI-GaAs, Si+-implanted and following rapid thermal annealing (RTA), were investigated, The PL spectra of Si-GA-C-As, Ga-i-Si-As, and V-As-Si-As were obtained. This paper concentrates on the PL peak at 1.36 eV which was proven as an emission of the Si-Ga-V-Ga combination by Si+ + P+ dual implantation. The results indicate that the peak at 1.36 eV appears when the ratio of As:Ga increased during the processing. Also high activation was obtained for the sample under the same conditions. More discussion on the mechanism of Si+ implanted SI-GaAs has been made based on the Morrow model [J. Appl. Phys, 64 (1988) 1889].

An introduction to the trapping of clusters with ion traps and electrostatic storage devices

This paper presents an introduction to the application of ion traps and storage devices for cluster physics. Some experiments involving cluster ions in trapping devices such as Penning traps, Paul traps, quadrupole or multipole linear traps are briefly discussed. Electrostatic ion storage rings and traps which allow for the storage of fast ion beams without mass limitation are presented as well. We also report on the recently developed mini-ring, a compact electrostatic ion storage ring for cluster, molecular and biomolecular ion studies.