Development of a PIGE-Detection System for in-situ Inspection and Quality Assurance in the Evolution of Fast Rotating Parts in High Temperature Environment Manufactured from TiAl

Intermetallic γ-titanium aluminides are a promising material in high temperature technologies. Their high specific strength at temperatures above 700°C offers the possibility for their use as components of aerospace and automotive industries. With a specific weight of 50% of that of the widely used Ni-based superalloys TiAl is very suitable as material for fast rotating parts like turbine blades in aircraft engines and land based power stations or turbocharger rotors. Thus lower mechanical stresses and a reduced fuel consumption and CO2-emission are expected. To overcome the insufficient oxidation protection the halogen effect offers an innovative way. After surface doping using F-implantation or liquid phase-treatment with an F-containing solution and subsequent oxidation at high temperatures the formation of a protective alumina scale can be achieved. By using non-destructive ion beam analyses (PIGE, RBS) F was found at the metal/oxide interface. For analysis of large scale components a new vacuum chamber at the IKF was installed and became operative. With this prototype of in-situ quality assurance system for the F-doping of manufactured parts from TiAl some performance test measurements were done and presented in this paper.Received: 01 March 2013; Revised: 24 April 2013; Accepted: 25 April 201

Angular momentum exchange during secular migration of two-planet systems

We investigate the secular dynamics of two-planet coplanar systems evolving under mutual gravitational interactions and dissipative forces. We consider two mechanisms responsible for the planetary migration: star-planet (or planet-satellite) tidal interactions and interactions of a planet with a gaseous disc. We show that each migration mechanism is characterized by a specific law of orbital angular momentum exchange. Calculating stationary solutions of the conservative secular problem and taking into account the orbital angular momentum leakage, we trace the evolutionary routes followed by the planet pairs during the migration process. This procedure allows us to recover the dynamical history of two-planet systems and constrain parameters of the involved physical processes.Comment: 20 pages, 9 figures, accepted for publication in Celestial Mechanics and Dynamical Astronomy (special issue on Exoplanets

Thermodynamic modeling of the CaO-SiO2-M2O (M=K,Na) systems

The aim of the present study is the CALPHAD modeling of the systems CaO-SiO2-M2O (M=K,Na) based on a careful review of the available literature data - phase diagram and thermodynamics - as well as own experiments. The heat capacities (Cp) of three compounds, CaSiO3, K2Ca2Si2O7 and K 8CaSi10O25 (determined using drop calorimetry), were included in the optimization of the ternary phase diagram CaO-SiO2-K2O

The role of multi-wall carbon nanotubes in char strength of epoxy based intumescent fire retardant coating

Fire resistance of coatings mostly depends on the formation of char. In this work Multi-wall carbon nanotubes (MWCNTs) were used to improve fire retardant and char properties of the intumescent coating. Different coating formulations were prepared and their heat shielding performance was tested at 950. °C according to ASTM E-119. Char expansion was studied using fire furnace test. Field emission scanning electron microscope was used for char morphology. By means of X-ray Diffraction and Fourier transform infrared spectroscopy the presence of carbon, borophosphate; boron oxide and sassolite in the char was identified. Thermogravimetric analysis results showed that 0.5. wt%MWCNTs enhanced the residual weight of char up to 29.35. wt%. X-ray photoelectron spectroscopy (XPS) confirmed that 0.5. wt% MWCNTs enhanced the carbon content up to 51.90. wt%, lowering oxygen content to approximately 25. wt% in the char that improved the fire resistance performance of the coating. Py rolysis analysis confirmed that 0.5. wt% MWCNTs formulation released less gaseous products and reduced the decomposition of gaseous products. An accelerated weathering test ASTM D 6695-03 also revealed that 0.5. wt% of MWCNTs sustained its reliability up to 90. days in accelerated weathering chamber

Hydrogen production via methane dry reforming process over CoAl and CoMgAl-Hydrotalcite derived catalysts

Co0.67Al0.31 and Co0.14Mg0.54Al0.31 hydrotalcite based catalysts were prepared by a coprecipitation method at a fixed pH=11, exhibiting a suitable hydrotalcite structure to be used as a catalyst in the reaction of the dry reforming of methane (DRM). Calcination at 450 °C provides the best conditions to prepare the most adapted structure and morphology to be later used in the DRM reaction. The samples were characterised by XRD, FTIR, SEM and it was shown that they exhibit a specific surface in the 30-70 g/cm² and a crystallite size of approximately 20 nm. The results of the TPR analysis showed clearly that CoAl-HT has better catalytic performances than CoMgAl-HT. This result can be explained by the presence of the Co0 for the catalyst CoAl-HTc-R and the total absence in the sample CoMgAl-HTc-R. The solid CoMgAl- HTc-R requires high reduction temperature compared to CoAl- HTc-R due to the strong CoO-MgO interactionsPeer reviewe

High temperature corrosion studies of a zirconia coating: Implications for waste-to-energy (WTE) plants

Corrosion of functional parts within waste-to-energy (WTE) plants significantly reduces their efficiency with respect to maintenance costs. Currently, nickel-based alloy claddings, several millimeters thick, are the state of the art as anti-corrosion coating. Another approach is to utilize thermally sprayed multilayer coatings with a zirconia top-coat. Lab-scale experiments under simulated WTE plant conditions and in situ tests within a WTE plant revealed a partially reduced porosity of the zirconia top-coat after the experiments, enabling the coating to act as a barrier against aggressive gases. In a lab-scale experiment sample the pores are filled up with zirconia, while the pores of the in situ samples are filled up with newly formed metal (Cr, Ni, Fe) oxides