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Organisationseinheit der BAM
The crystallization behavior of sodium ion conductive Na2MnP2O7 glass was examined to clarify the crystallization mechanism. The formation of thermodynamically metastable phase, layered Na2MnP2O7, at the surface of the glass occurred. Heat treatment at 430 °C for 3 h lead to surface crystals of Na2MnP2O7 oriented with the (101) direction perpendicular to the sample surface. As the heat treatment temperature increased, the glass-ceramic samples deformed, and the presence numerous micro bubbles due to dissolved water was detected.
Ceramics and their composites are in general brittle materials because they are predominantly made up of ionic and covalent bonds that avoid dislocation motion at room temperature. However, a remarkable ductile behavior has been observed on newly developed 11 mol.% ceria-stabilized zirconia (11Ce-TZP) composite containing fine alumina (8 vol.% Al2O3) and elongated strontium hexa-aluminate (8 vol.% SrAl12O19) grains. The as-synthesized composite also has shown full resistance to Low Temperature Degradation (LTD), relatively high strength and exceptionally high Weibull modulus, allowing its use in a broader range of biomedical applications. In this study, to deepen the understanding of plastic deformation in Ce-TZP based composites that could soon be used for manufacturing dental implants, different mechanical tests were applied on the material, followed by complete microstructural characterization. Distinct from pure Ce-TZP material or other zirconia-based ceramics developed in the past, the material here studied can be permanently strained without affecting the Young modulus, indicating that the ductile response of tested samples cannot be associated to damage occurrence. This ductility is related to the stress-induced tetragonal to monoclinic (t-m) zirconia phase transformation, analogue to Transformation-Induced Plasticity (TRIP) steels, where retained austenite is transformed to martensite. The aim of this study is to corroborate if the observed plasticity can be associated exclusively to the zirconia t-m phase transformation, or also to microcraking induced by the transformation. The t-m transformed-zones produced after bending and biaxial tests were examined by X-ray refraction and SEM/TEM coupled with Raman. The results revealed that the observed elastic-plastic behavior occurs without extensive microcracking, confirming a purely elastic-plastic behavior driven by the phase transformation (absence of damage).
Glasses with compositions of 21Gd2O3-63MoO3-(16-x)B2O3-xTeO2 (mol%) (x= 0, 2, 4, 8) were prepared using a conventional melt quenching technique, and the crystallization behavior of ferroelastic β′-Gd2 MoO4)3 Crystals was examined to clarify the mechanism of self-powdering phenomenon and to design bulk crystallized glasses. It was found that the self-powdering phenomenon appeared significantly during the crystallization at temperatures near the crystallization peak temperature, but the phenomenon is suppressed in the crystallization at temperatures much higher than the glass transition temperature. It was also found that the substitution of TeO2 for B2O3 in the base glasses suppresses the self-powdering phenomenon and consequently bulk crystallized glasses were obtained in the glass with x=8 mol%. The densities at room temperature of the base glasses are d =4.755–4.906 g/cm3, being much higher than the value of d=4.555 g/cm3 for β′-Gd2(MoO4)3 crystal. It is proposed that the stresses in the inside of crystals induced by large density differences (i.e., large molar volume differences) between the glassy phase and crystals might be relaxed effectively in the glasses containing TeO2 with weak TeeO bonds and fragile character.
Mobility particle size spectrometers (MPSS) belong to the essential instruments in aerosol science that determine the particle number size distribution (PNSD)in the submicrometer size range. Following calibration procedures and target uncertainties against standards and reference instruments are suggested for a complete MPSS quality assurance program: a) calibration of the CPC counting efficiency curve (within 5% for the plateau counting efficiency; within 1 nm for the 50% detection efficiency diameter), b) sizing calibration of the MPSS, using a certified polystyrene latex (PSL) particle size standard at 203 nm (within 3%), c) intercomparison of the PNSD of the MPSS (within 10% and 20% of the dN/dlogDP concentration for the particle size range 20 – 200 nm and 200 to 800 nm, respectively), and d) intercomparison of the integral PNC of the MPSS (within 10%). Furthermore, following measurement uncertainties have been investigated: a) PSL particle size standards in the range from 100-500nm match within 1% after sizing calibration at 203 nm. b) Bipolar diffusion chargers based on the radioactive nuclides Kr85, Am241 and Ni63 and a new ionizer based on corona discharge follow the recommended bipolar charge distribution, while soft X-ray-based charges may alter faster than expected. c) The use of a positive high voltage supply show a 10% better performance than a negative one. d) The intercomparison of the integral PNC of an MPSS against the total number concentration is still within the target uncertainty at an ambient pressure of approximately 500 hPa.
3-Aminovinylquinoxalines are readily accessible from (hetero)aryl glyoxylic acids or heterocyclic π-nucleophiles by consecutive four- and fivecomponent syntheses in the sense of an activation-alkynylation-cyclocondensation-addition sequence or glyoxylation-alkynylation-cyclocondensation-addition sequence in good yields. The title compounds are highly fluorescent with pronounced emission solvatochromicity and protochromic fluorescence quenching. Time-resolved fluorescence spectroscopy furnishes radiative and nonradiative fluorescence decay rates in various solvent polarities. The electronic structure is corroborated by DFT and TD-DFT calculations rationalizing the observed spectroscopic effects.
Die Berechnung von Wärmebrücken unter stationären und instationären Randbedingungen, die Optimierung von Wärmespeichern, die Beurteilung sowohl wärmeschutz- als auch brandschutztechnischer Maßnahmen und Energiebedarfsrechnungen setzen die Kenntnis thermischer Eigenschaften, u.a. der Wärmeleitfähigkeit Lambda und der spezifischen Wärmekapazität c, in Abhängigkeit der Temperatur voraus. Im Rahmen einer Zusammenarbeit der EMPA-Dübendorf und der BAM-Berlin wurde ein Kurzzeit-Prüfverfahren mit anschließender numerischer Auswertung entwickelt, das eine simultane Bestimmung dieser beiden Größen ermöglicht. In dem Band wird über das Kurzzeit-Prüfverfahren, das numerische Auswerteverfahren und die Resultate der Messungen an einigen ausgewählten Baustoffen berichtet.
The therapy of eye tumors with fast protons is an excellent tool giving very high local control rates. At the Helmholtz-Zentrum Berlin (HZB) almost 1800 patients were treated since 1998. A 2 MV Tandetron was installed as injector for the k = 132 HZB cyclotron. Using the standard 358 duoplasmatron ion source with direct extraction of negative hydrogen ions an extremely stable proton beam can be delivered, both on the short-term and the long-term scale. The hair-needle filaments made from thoriated tungsten wires have safe operation times of more than 1000 h.
The material properties of recycled concrete aggregates (RCA) are
correlated to the sorting accuracy of the former demolition waste. Impurities like
wood, clay bricks or gypsum can lead to inferior building material properties. Harmful
substances like heavy metals or organic pollutants should be minimised as well.
Hence the non-concrete materials have to be separated from the concrete material
stream. This can be done during the demolition process by using selective
dismantling techniques. Alternatively a variety sorting and classifying techniques to
purify the crushed concrete can be utilized.
A research project, funded by the Federal Ministry for the Environment, Nature
Conservation and Nuclear Safety, investigated the possibilities of gaining recycled
concrete aggregates of a high quality for the reuse in the production of concrete. The
work focuses especially on how gypsum respectively sulphates in the crushed
concrete can be reduced. Sulphates can impair the setting behaviour of concrete
and also damage set concrete by causing expansion. Therefore the content of
sulphates in RCA is restricted by guidelines and standards in Germany.
Generally, gypsum in construction waste originates from interior fittings like gypsum
walls, floor screeds, plaster boards and also plaster. Most of these materials can be
reconstructed using selective dismantling techniques. This can be achieved either by
manual labour or by using mechanical equipment e.g. to remove floor screeds by
milling. Depending on the specific deconstruction site it can be more effective and/or
more environmentally compatible to remove sulphates by treating the crushed
concrete. Applicable treatments for sulphate reduction include dry processes like
manual sorting of gypsum wall blocks as well as wet treatments e.g. jigging.
In addition this research project an environmental performance evaluation was
undertaken to assess different techniques for reducing sulphates in recycled
concrete aggregates.
Zur Untersuchung der Initiierungsvorgänge und dem Wachstumsverhalten lokaler Korrosionskeime auf nichtrostenden Stählen wurde eine neue elektrochemisch-mikroskopische Messmethode entwickelt. Bei dieser Messmethode wird durch Einsatz eines Echtfarben- Konfokalmikroskops mit Immersionsobjektiv das empfindliche elektrochemische Rauschmessverfahren um eine bildgebende Messkomponente erweitert. Ziel dieser Untersuchung war es, diskrete Rauschmesssignale visuell detektierbaren Korrosionserscheinungen auf der Stahloberfläche nahezu in Echtzeit zuzuordnen. Auf Grund der notwendigen Anforderungen an einen in situ Messaufbau wurde im Rahmen dieser Untersuchung ein neuartiges selbstklebendes Folienelektrodensystem, bestehend aus Gegen- und Bezugselektrode, entwickelt, das für die in situ Messung zum Einsatz kam. Die in situ Untersuchungen wurden an dem austenitischen Chrom-Nickel-Stahl 1.4301 durchgeführt. Als Ergebnis der Experimente konnten Stromtransienten im nA- bis μA-Bereich messtechnisch erfasst werden und mikroskopisch kleinen Korrosionskeimen, die sowohl stabil wie auch metastabil auf der Stahloberfläche auftraten, diskret und zeitnah zugeordnet werden. Weiterhin konnten mit Hilfe der Konfokaltechnik die Volumina und die Mantelflächen der einzelnen Lochdefekte ermittelt werden, sodass durch Auswertung und Kombination der elektrochemischen und mikroskopischen Messergebnisse erstmalig die Korrosionsstromdichte bestimmt werden konnte, die bei der Initiierung der lokalen Lochkeime aufgetreten ist. Damit konnte die Funktionalität und die hohe Empfindlichkeit des elektrochemisch-mikroskopischen Messverfahrens im Rahmen dieser Untersuchung erfolgreich verifiziert werden.
Nanotechnologie im Bauwesen
(2008)
Zu den Zielen der Nanotechnologie gehört die Entwicklung, Produktion und Anwendung von Materialien und Werkstoffen mit völlig neuartigen Leistungsspektren. Für die Baupraxis und die Materialforschung lassen sich über den Einsatz der Nanotechnologie Ziele wie die Optimierung von Baustoffeigenschaften, Vermeidung von Schäden und neue Funktionalitäten definieren. Der vorliegende Beitrag gibt einen Überblick über mögliche Anwendungsbereiche der Nanotechnologie im Bausektor, wie z. B. zementgebundene Baustoffe, Außen- und Dachfassaden, Fenster und Verglasungen, Brandschutz, Inneneinrichtung und Infrastrukturbau. Zudem werden aktuelle Forschungsarbeiten mit nanowissenschaftlichem und nanotechnologischem Schwerpunkt im Bereich baustoffbezogener Materialien der Bundesanstalt für Materialforschung und -prüfung (BAM) in Berlin vorgestellt. Die Forschungstätigkeiten beziehen sich zum einen auf die Modifikation der Hydratphasen in Ultra-Hochleistungsbeton (UHPC) und zum anderen auf die Weiterentwicklung von Anti-Graffiti-Systemen.
The total reliability of a mine searching system is driven by the triple of intrinsic
capability, which describes the physical-technical basis capability, the application and
environmental factors and the human factors. Some of them can be determined in
laboratory measurements but the human factor and a part of environment conditions
and their interaction with the device need to be treated statistically. That is why the
test & evaluation procedure described in CEN CWA 14747:2003, includes in addition
to parameter tests of metal detectors also the reliability or blind field tests under local
conditions with local personnel. A series of three big field trials had been
accomplished in the ITEP-project 2.1.1.2 Reliability Model for Test & Evaluation of
Metal Detectors to specify the optimum conditions for reliable trial results with
affordable effort. For each set of specific working conditions, characterized in terms
of a combination of one mine type in one soil with one detector handled by local
personnel, the searching system will show up a working performance in mine
detection rates as a function of mine depth and show up a certain overall false call
rate. During the ITEP-trials in Benkovac and Oberjettenberg the authors learnt to
determine this function separately for each mine type in each soil, which is especially
important for low metal mines in uncooperative soil which will be illustrated for the
mine PMA2 in different types of soil. The question of representativeness for field
conditions on the one hand and necessary statistical set up for the possibility to
distinguish between individual detector performances is still under discussion.
Aufgrund der großen Massenströme ist das Recycling von Baurestmassen von besonderer Bedeutung
für die Schonung von natürlichen Ressourcen. Eine wichtige Voraussetzung für ein hochwertiges
Recycling, wie z.B. eine Wiederverwertung von aufbereitetem Bauschutt/Altbeton als rezyklierte
Gesteinskörnung im Hochbau, ist die Einhaltung von Grenzwerten für Stör- und Schadstoffe. Dabei
steht der Sulfatgehalt im Eluat von Bauschutt besonders im Fokus. In der vorliegenden Studie wird
untersucht, wie durch die Optimierung von Abbrucharbeiten und Bauschuttaufbereitung hochwertige
Gesteinskörnungen aus Altbeton gewonnen werden können. Anhand von Literatur- und
Datenrecherchen werden zunächst Sulfatquellen in Gebäuden sowie verfügbare Abbruch- und
Aufbereitungstechniken zusammengestellt. Am Beispiel von unterschiedlichen Gebäudetypen werden
Szenarien für selektiven und nicht selektiven Abbruch (Schwerpunkt: Sulfatentfachtung) in Hinblick auf
ihre Umweltwirkungen ökobilanziell bewertet. Ergänzt werden diese Bewertungen durch
Untersuchungen an realen Bauschuttmaterialien und Abbruchprojekten. Auf dieser Basis werden
Handlungsempfehlungen für die Gewinnung von hochwertigen RC-Gesteinskörnungen erarbeitet und
diskutiert.-----------------------------------------------------------------------------------------
Due to the large-scale mass flow of construction and demolition wastes, the recycling of those
residues is of particular importance for the conservation of natural resources. An important
requirement for recycling on a high level, like the reuse of crushed concrete as recycled concrete
aggregate, is the observation of limits for hazardous substances and impurities. This study is focusing
on the reduction of sulphates in the eluate of crushed concrete. An investigation of possibilities to
optimize demolition and dismantling as well as treatment of crushed concrete with the objective of
gaining recycled concrete aggregates of high quality. Based on a literature research and a data review
the origins of sulfates in buildings and also the availability of techniques for demolition and treatment
of crushed concrete are listed and evaluated. Using the examples of different building types scenarios
for selective dismantling and non-selective demolition (focused on reducing suphates) are evaluated in
terms of affecting the environment. In addition samples from real demolition construction sites and
plants for treatment of construction rubble were investigated. Based on these results
recommendations for the production of high quality recycled concrete aggregates are worked out.
The paper presents technical details of the drop test performance as well as some experimental results of tests carried out with the Japanese 'Yoyushindo-disposal' waste container for intermediate depth disposal. The tests were accompanied by various metrology to collect data as basis for safety assessment.
We report the sintering of 3D-printed composites of 13-93 bioactive glass and hydroxyapatite (HAp) powders. The sintering process is characterized on conventionally produced powder compacts with varying HAp content. A numeric approximation of the densification kinetics is then obtained on the basis of Frenkel, MackenzieShuttleworth, and EinsteinRoscoe models, and optimized sintering conditions for 3D-printed structures are derived. Fully isotropic sintering of complex cellular composites is obtained by continuous heating to 750°C at a rate of 2 K/min for a HAp content of 40 wt%. The approach can readily be generalized for printing and sintering of similar glass-ceramic composites.
A detailed characterization of metal-tagged antibodies is the prerequisite for the implementation of quantitative concepts in inductively coupled plasma–mass spectrometry (ICP-MS)-based bioanalysis or future medical diagnosis. In this paper, the common modification with bifunctional ligands containing maleimide residues as a reactive group was investigated in detail via size exclusion chromatography (SEC)-ICP-MS and liquid chromatography–time-of-flight (LC-TOF)-MS to determine the preservation of the antibody structure after tagging. Mouse monoclonal IgG modified with metal-coded tags (MeCATs) was used as a model system. Several antibody fragments were identified carrying different numbers of metal tags. In a second step, a functionality test was performed with isolated fragments where the antigen specificity was tested in a dot blot immunoassay.
Kunststoff- und Kunststoffrasenflächen kommt bei intensiv genutzten Flächen als Allwetterbeläge eine große Bedeutung zu. Sie leisten einen wichtigen Beitrag zur Absicherung eines ganzjähriger Sportangebote.
Gerade Kunststoffrasen ist aber in den letzten Jahren häufig in die Kritik geraten, insbesondere durch gefährliche Inhaltsstoffe und andere negative Einflüsse auf die Umwelt. Dies hat bei Bauherren zu einer Verunsicherung geführt und Fragen aufgeworfen, die erst teilweise beantwortet sind. Die Diskussionen rund um diesen Allwetterbelag haben bereits dazu geführt, dass von Seiten der Industrie viel verändert wurde und neue innovative Lösungen gefunden werden.
Der Fachbericht stellt eine Handreichung für Fachleute und interessierte Laien dar, um mehr Klarheit besonders hinsichtlich der Umweltanforderungen zu erzielen.