672 research outputs found

    Manufacturing, Composition, Properties and Application of Sintered Hard Metals

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    Among other materials, hard metals represent an important family of functional materials. They show properties that are combinations of those of their constituents. The general idea while using hard metals is to exploit their excellent properties in terms of hardness, toughness, wear resistance, and chemical stability. These characteristics made hard metals as promising candidate for use as a cutting tool, which constitutes their main area of application. Depending on the particular use, the most important properties can be achieved: (i) by properly selecting the constituents made up the whole composition, (ii) by varying the relative composition of the phases, or (iii) by applying a suitable hard metal coating layer on the top of the cutting tool. This chapter presents a general overview of the actual scenario concerning different tool materials, including a short history and description of state‐of‐the‐art techniques as regards their composition, their manufacturing routes and their most important properties. Some results of the own research in this field are carried out during the years will integrate this part

    Bio-compatibility of metallic alloys for body-area communication systems

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    Mechanical behavior, biocompatibility in body environment and tissues and chemical stability are the most important requirements for the effective application of any bio-implant materials in the human body. Among the known metals and alloys, stainless steels, CoCr alloys and Ti and its alloys are the most widely used materials in such applications. In case of their use, one of the most important engineering approach is to guarantee insignificant biological stress to the human system and to maintain the whole integrity and functionality of the human being. In this paper we pay our attention on the study of the properties of two types of metallic alloys: one of them is a modified CoCr alloy, while the second one is a new generation of TiNb based alloy. The first step of the study is related to the determination of the microstructural and mechanical behavior of the alloys and to assess their chemical stability by the evaluation of their corrosion resistance. The further step will be to evaluate and to control the interaction between the human body and the biomaterial inside the biological environment using an appropriate numerical model. In this way it will be possible to detect the presence of defects in the biomaterial, considering the surface chemistry and its topography, which can control this system leading to regulate in time an inappropriate interface avoiding the removal of the implant for the restoration. Furthermore, the results of such an investigation represent a good starting point in designing of intra-, inter-body or body-coupled printed implanted antennas, i.e., antennas located inside the body used to communicate with external base stations or between different nodes of a network

    Light Alloys — From Traditional to Innovative Technologies

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    Selection of materials with the expected, application-dependent characteristics constitutes a very important point in any industrial application. In the automotive and aeronautical industries, the current tendency is to use light metals and their alloys for production of various components. For example, some of the problems related to fuel consumption and weight reduction could be partially solved by using such alloys as an alternative to traditional iron-based alloy components. Due to their very attractive properties, the most commonly employed light materials for producing high-stressed components are aluminium, magnesium and their alloys. Al-based alloys have a high strength/weight ratio, good formability, excellent combination of castability and mechanical properties which together with an excellent corrosion resistance make them very appropriate for a large variety of applications. There are two important families of aluminium alloys: (i) wrought alloys, firstly cast as ingots and/or billets and then mechanically hot- and/or cold-worked into the preferred shape, and (ii) cast alloys, directly cast into their final form through different traditional or innovative processes

    Up-to-Date Knowledge and Outlooks for the Use of Metallic Biomaterials: Review Paper

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    In all cases, when a material has to be used in medical applications, the knowledge of its physical, chemical and biological properties is of fundamental significance, since the direct contact between the biological system and the considered device could generate reactions whose long-term effects must be clearly quantified. The class of materials that exhibits characteristics that allow their use for the considered applications are commonly called biomaterials. Patients suffering from different diseases generate a great demand for real therapies, where the use of biomaterials are mandatory. Commonly, metallic biomaterials are used because their structural functions; the high strength and resistance to fracture they can offer, provide reliable performance primarily in the fields of orthopedics and dentistry. In metals, because of their particular structure, plastic deformation takes place easier, inducing good formability in manufacturing. The present paper is not encyclopaedic, but reports in the first part some current literature data and perspectives about the possibility of use different class of metallic materials for medical applications, while the second part recalls some results of the current research in this field carried out by the authors

    Investigations on coating of dies for advanced squeeze casting process

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    Abstract Premature failure of dies is a critical problem of manufacturers in hot-working processes, e.g. metal die casting, hot extrusion and/or thixoextrusion of aluminium/magnesium or steel. Typically, die material has to be resistant to heat cycling or corrosion environment, to plastic deformation and wear, especially when exposed to high temperature during continuous working cycle. The resistance of dies could be increased by the modification of their surfaces, i.e. by the application of an adequate coating. An improvement of the resistance of H11 steel substrate will be presented and discussed. Here, the coatings will be realized through both by High Velocity Oxy-Fuel coating spray method and by plasma spray method. Firstly, the measurement of the residual stress will be carried out on the un-coated and coated substrate. Secondly, morphological analysis by optical and scanning electron microscopy will be performed on the powders used for the coating and on the coated materials. Such investigations aim finding the most favourable conditions, as concern the materials to be employed for the deposition and the more appropriate deposition techniques, in order to achieve improved properties for the dies which can be used in innovative casting techniques, i.e. squeeze casting and/or some related modified processes

    Evaluation verschiedener Technologien als saisonale Wärmespeicher fßr Solarthermie und Wärmepumpen als Wärmeerzeuger

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    Diese Masterthesis wurde in der Forschungsgruppe Erneuerbare Energien der Master Research Unit Ecological Engineering an der ZHAW in Wädenswil durchgefßhrt. Das Ziel der Arbeit war, es bezßglich der verwendeten Wärmespeichertechnologie verschiedene kombinierte Heiz- und Kßhlsysteme fßr den Einsatz in Gebäuden mit einem jährlichen Heizwärmebedarf von mehr als 20 MWh, als Alternativen zu Systemen mit Erdwärmesonden, L/W WPs oder Holzfeuerungen zu finden. Die Systeme sollen ßber eine PVT-Anlage zur Strom- und Wärmegewinnung, einem saisonalen Pufferspeicher fßr die Wärme aus den PVT-Kollektoren sowie einer Sole/Wasser-Wärmepumpe als Wärmeerzeuger verfßgen. In der Recherche zu den verfßgbaren Speichertechnologien wurde ersichtlich, dass vor allem der eTank, der Eisspeicher sowie der Paraffin-Speicher als potenziell geeignete Speichertechnologien fßr den Einsatz als Wärmespeicher im vorgegebenen System eingestuft werden. Bei einem eTank handelt es sich um einen ins Erdreich eingelassenen sensiblen Wärmespeicher, der mit einem Fßllmaterial wie Erde, Sand oder Kies gefßllt ist, und je nach Bedarf mit Wärme beladen oder Wärme daraus entzogen werden kann. Mit den ausgewählten Speichertechnologien wurden folgende fßnf kombinierten Heiz- und Kßhlsysteme zur näheren Betrachtung definiert: eTank System, 2-eTank System, Eisspeicher System, Paraffin-Speicher System und Paraffin-Speicher + eTank System. Anschliessend wurden die Systeme anhand ihrer Eignung zum Einsatz in verschiedenen Gebäudetypen mittels Simulationsresultaten aus Polysun bewertet und mit einander verglichen. Die Gebäudetypen wurden durch ihren jährlichen Heizwärmebedarf und anhand der Unterscheidung zwischen Neubauten und Sanierungsgebäude charakterisiert. Mit den Simulationsresultaten wurde fßr jedes System eine Dimensionierungsmatrix erstellt, die eine Aussage darßber liefert, ob und wie gut sich ein bestimmtes Heiz- und Kßhlsystemen fßr einen bestimmten Gebäudetyp eignet und mit welcher SpeichergrÜsse, welcher Anzahl an PVT Kollektoren und welcher Systemjahresarbeitszahl (SJAZ) zu rechnen ist

    GABI-Kat SimpleSearch: an Arabidopsis thaliana T-DNA mutant database with detailed information for confirmed insertions

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    Insertional mutagenesis approaches, especially by T-DNA, play important roles in gene function studies of the model plant Arabidopsis thaliana. GABI-Kat SimpleSearch () is a Flanking Sequence Tag (FST)-based database for T-DNA insertion mutants generated by the GABI-Kat project. Currently, the database contains >108 000 mapped FSTs from ∟64 000 lines which cover 64% of all annotated A.thaliana protein-coding genes. The web interface allows searching for relevant insertions by gene code, keyword, line identifier, GenBank accession number of the FST, and also by BLAST. A graphic display of the genome region around the gene or the FST assists users to select insertion lines of their interests. About 3500 insertions were confirmed in the offspring of the plant from which the original FST was generated, and the seeds of these lines are available from the Nottingham Arabidopsis Stock Centre. The database now also contains additional information such as segregation data, gene-specific primers and confirmation sequences. This information not only helps users to evaluate the usefulness of the mutant lines, but also covers a big part of the molecular characterization of the insertion alleles

    Gestione delle anime inorganiche nell’industria fusoria dell’alluminio: stato dell’arte

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    Nell’industria fusoria dell’alluminio il tema della gestione delle anime da fonderia è di particolare rilievo. L’obiettivo dell’azzeramento delle emissioni inquinanti in atmosfera, in un’ottica di impatto ambientale eco-friendly, ha fatto sì che sia tendenza crescente nelle fonderie l’adozione di anime basate su sistemi di leganti inorganici. In presenza di alti volumi produttivi di componenti ottenuti tramite colata in conchiglia permanente, le anime a legante inorganico sono da prediligere in quanto permettono di eliminare emissioni nocive e migliorare la produttività complessiva dell’impianto. Tuttavia, l’adozione di tali anime comporta la necessità di adottare particolari accorgimenti al fine di garantirne il loro corretto utilizzo, ottimizzando così il processo di colata. Infatti, l’igroscopicità di questa tipologia di anime può creare importanti difettologie in fase di colata dei getti, nonché indebolimento delle anime e loro possibile frattura, spostamento o deformazioni in fase di colata. L’obiettivo di questo lavoro è presentare uno stato dell’arte sull’attualità industriale, relativo alle fonderie di alluminio, in termini di adozione di anime realizzate con sistemi leganti inorganici, loro gestione e possibili difetti nei getti ad esse correlati. Tale stato dell’arte sarà tale da guidare il più possibile verso i know-how necessari ad ottimizzare al meglio gestione ed adozione delle anime
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