Correlations between microstructural characterization and thermal properties of well defined poly(ε-caprolactone) samples by ring opening polymerization with neutral and cationic bis(2,4,6-triisopropylphenyl)tin(IV) compounds

In this paper a study of correlations between the microstructure of well defined poly(ε-caprolactone) (PCL) samples and their physical properties such as thermal degradation, crystallization kinetics and melting behavior is described. The PCL samples were obtained in the presence of the compound benzyl-methoxy-bis(2,4,6-triisopropylphenyl)tin (1), acting as single-site and living initiator, as well as in the presence of compounds Tip₂SnRR′ [Tip = 2,4,6-triisopropylbenzene; R = R′ = CHCH₂ (2); R = CH₂Ph, R′ = Br (3)] activated by ionizing agents. PCL samples having different end groups, molecular weight and molecular weight distribution were obtained. The samples were fully characterized by GPC and NMR. The thermal degradation of the synthesized samples were studied by thermogravimetric analysis (TGA) in air flow. The experimental results suggested that the presence of ester chain end groups has a beneficial effect on the thermal stability of the PCL samples, independently on the molecular weights and molecular weight distribution. The crystallization behavior was studied in isothermal conditions at 37 °C, 40 °C, and 43 °C through differential scanning calorimetry (DSC). In this case, either the molecular weight (M_w) or the polydispersivity index (PDI) have a significant effect on the kinetics of crystallization of PCLs.     

Advantage of redundancy in the controllability of remote handling manipulator

To carry out a variety of remote handling operations inside the ITER divertor a Water Hydraulic MANipulator (WHMAN) and its control system have been designed and developed at Tampere University of Technology. The manipulator is installed on top of Cassette Multifunctional Mover (CMM) to assist during the cassette removal and installation operations. While CMM is designed to carry heavy components such as cassettes through the service ducts relying on positioning accuracy and repeatability, WHMAN is designed to execute a mix of remote handling operations using position trajectories and master-slave telemanipulation. WHMAN is composed of eight joints: six rotational and two translational. Since a manipulator requires only six joints to acquire the desired position and orientation in operational-space, the two additional joints of WHMAN provide the redundant degrees of mobility. This paper presents how this redundancy of WHMAN can be an advantage to optimize the execution of remote handling tasks. The paper also discusses an effective way to practically exploit the redundancy. The results show that the additional degrees of freedom can be utilized to improve the dynamic behavior of the manipulator.     

Powder Injection Molding – An innovative manufacturing method for He-cooled DEMO divertor components

At Karlsruhe Institute of Technology (KIT), a He-cooled divertor design for future fusion power plants has been developed. This concept is based on the use of modular cooling fingers made from tungsten and tungsten alloy, which are presently considered the most promising divertor materials to withstand the specific heat load of 10 MW/m². Since a large number of the finger modules (n > 250,000) are needed for the whole reactor, developing a mass-oriented manufacturing method is indispensable. In this regard, an innovative manufacturing technology, Powder Injection Molding (PIM), has been adapted to W processing at KIT since a couple of years. This production method is deemed promising in view of large-scale production of tungsten parts with high near-net-shape precision, hence, offering an advantage of cost-saving process compared to conventional machining.The complete technological PIM process for tungsten materials and its application on manufacturing of real divertor components, including the design of a new PIM tool is outlined and, results of the examination of the finished product after heat-treatment are discussed. A binary tungsten powder feedstock with a solid load of 50 vol.% was developed and successfully tested in molding experiments. After design, simulation and manufacturing of a new PIM tool, real divertor parts are produced. After heat-treatment (pre-sintering and HIP) the successful finished samples showed a sintered density of approximately 99%, a hardness of 457 HV0.1, a grain size of approximately 5 μm and a microstructure without cracks and porosity.     

Automobile shredded residue valorisation by hydrometallurgical metal recovery

The aim of this work was developing a hydrometallurgical process to recover metals from automobile shredded residue (or car fluff). Automobile shredded residue (ASR) was characterised by particle size distribution, total metal content and metal speciation in order to guide the choice of target metals and the operating conditions of leaching. Characterisation results showed that Fe is the most abundant metal in the waste, while Zn was the second abundant metal in the fraction with diameter lower than 500 μm. Sequential extractions denoted that Zn was easily extractable by weak acid attack, while Fe and Al required a strong acid attack to be removed. In order to recover zinc from <500 μm fraction leaching tests were operated using acetic acid, sulphuric acid and sodium hydroxide at different concentrations. Sulphuric acid determined the highest zinc extraction yield, while acetic acid determined the highest zinc extractive selectivity. Sodium hydroxide promoted an intermediate situation between sulphuric and acetic acid. Zn recovery by electro winning using acetic leach liquor determined 95% of Zn electro deposition yield in 1h, while using sulphuric leach liquor 40% yield in 1h and 50% yield in 2h were obtained. Simulation results showed that the sulphuric leaching process was more attractive than acetic leaching process.     

Synthesis of biodiesel from edible,non-edible and waste cooking oils via supercritical methyl acetate transesterification

The use of methyl acetate instead of methanol for supercritical synthesis of glycerol-free biodiesel from vegetable oils is a new process and its study is very limited in the literature. In this work, it has been tested for the first time on three edible and non-edible oils with different fatty acid composition. The process was also applied to waste oil with higher free fatty acid (FFA) content. The results demonstrate that the oil composition does not significantly influence the biodiesel yield.The influence of temperature, pressure and molar ratio of reactants was studied. All the oils achieved complete conversion after 50 min at 345 °C, 20 MPa with methyl acetate:oil molar ratio equal to 42:1. The obtained data also allowed calculating the apparent rate coefficients and activation energies.Eventually, some new information on the process was obtained. Thermal degradation of triacetin, which substitutes glycerol as the by-product of the transesterification reaction, was observed. Some indicative experiments were performed to understand the role of the acetic acid produced by FFA esterification.     

Chemistry Constraints on the Origin of Life

This analysis starts from the view that prebiotic chemical evolution, leading to the first forms of life on earth, was based on a series of sequential steps, each determined by its own contingent initial conditions. This view is opposed to the more established one, which sees the origin of life as a series of preordered series of events, where each one is deterministically caused by the previous one and causally determines the next one. Some of the main constraints of chemistry that affect such prebiotic chemical evolution are examined. The notion of contingency is seen as a very important organizing process subjected to chemistry, whereby contingency also responds to a certain degree of determinism. Kinetic control, as another determinant and constraint of the prebiotic evolutionary process, can be critically important and, at a certain point of the chemical evolutionary process, kinetic control in the form of catalysis will become essential. Simple peptides can be considered as the first catalysts, at least for the condensation of peptide bonds. The concentration threshold for prebiotic reactions is often not taken into account in the literature, particularly in the field of the prebiotic RNA world. In addition, this shortcoming can make the entire prebiotic RNA world construction shaky and unreliable, including the “myth” of the perennial self-replication of an RNA macromolecule. The general question of self-replication and the problem of homochirality are also briefly discussed. Although these chemical constraints may hinder the reconstruction of life as it is now in the laboratory, their understanding can be useful and even essential for devising a synthetic alternative route to functional macromolecules and to their metabolic interactions.     

Closed‐form method for the reconstruction of 2‐D objects: Preliminary experimental results

An analytical approach to inverse electromagnetic scattering is tested on 2‐D experimental data. The closed‐form singular value decomposition of the scattering integral operator is the basis for determining the radiating components of the equivalent source density. This equivalent source is used to reconstruct the features of a scatterer. Reconstructions performed on different scattering data show the capabilities of the method and, thanks to the closed‐form solution, results are available after a very short time of computation. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.