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Eingeladener Vortrag
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Investigations of Polymer Heterogeneity by Two-Dimensional HPLC, MALDI-TOF-MS and FTIR Coupling
(1995)
Untersuchungen zur Charakterisierung des Abbaus von Polylactiden mittels 2D-HPLC und MALDI-TOF-MS
(1995)
Struktur des basischen Zink-O,O'-ethylhexyldithiophosphats in unpolar, aprotischen Lösungsmitteln
(1995)
Was ist wie und wo geregelt?
(1995)
Eine rechnergesteuerte Apparatur zur Bestimmung der Explosionsgrenzen von Gasen und Gasgemischen
(1995)
A series of 2-functional 1,3-dioxa-2,4,7-trisilacycloheptanes was synthesized and characterized by means of 29Si NMR spectroscopy, gas chromatography, high performance liquid chromatography and gas chromatography-mass spectrometry. The signals were assigned to the various configurational isomers. This assignment was confirmed by independent synthesis of individual isomers. The sequence of the NMR signals of the all-cis and trans-trans isomers required for the determination of stereochemistry was found to be the same as that of the respective cyclotrisiloxanes.
A mixture of linear and cyclic methylsiloxanes was analysed to characterize the different types of siloxane structures using gas chromatography (GC), mass spectrometry (MS) and Fourier transform infrared (FT-IR) spectroscopy. Siloxane structures are formed by hydrolysis of dimethyldichlorosilane under controlled conditions in technical applications. In the presence of methyltrichlorosilane or even trimethylchlorosilane, linear polydimethylsiloxanes and mono-, bi- or polycyclic methylsiloxanes are synthesized depending on the reaction conditions. The main structural units are (CH3)3SiO1, (CH3)2SiO and (CH3)SiO3. GC-MS may provide molecular mass information, but it is not able to identify isomeric structures, which are also formed in lower quantities by the mentioned reactions. Coupling GC with FT-IR enables the determination of group frequencies to assign specific structures. Thus, combination of GC with MS and FT-IR may be used in elucidating complex cyclosiloxane compounds. FT-IR measurements were performed with a Tracer unit.
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.
27Al nuclear magnetic resonance spectra of polycrystalline aluminium borate 9Al2O3 · 2B2O3 have been measured in double rotation at 11.7 and 7.0 T and high-speed magic-angle spinning at 7.0, 9.4, 11.7, 14.1 and 17.6 T. Spinning sidebands from the satellite transitions were observed at 7.0 and 14.1 T. Each of the four structural aluminium sites [Al(IV), Al(V)(1), Al(V)(2) and Al(VI)] are observed, characterised and assigned in the spectra. The obtained parameter set gives a fully consistent interpretation in agreement with the crystal structure of the compound.
Barrier properties of plasma and chemically fluorinated polypropylene and polyethyleneterephthalate
(1995)
The functionalization, perfluorination or an coating of polypropylene (PP) and polyethyleneterephthalate (PET) surfaces in different plasma atmospheres and in an F[2] + N[2] gas mixture were investigated. The aim of this work was to form a barrier layer against solvent and fuel permeation. Typical test solvents were n-pentane, toluene, tetrachloroethylene and mixtures of n-pentane and methanol. The permeation was gravimetrically measured. The permeation of the solvent mixtures was analyzed by mass spectrometry and Fourier transform IR spectroscopy. The permeation of the solvent mixtures through the plasma-modified polymer samples was associated with increased absorption of polar solvent components in the polymer film. The thickness of the plasma-fluorinated PP surface layer was 10-100 nm and that of chemically fluorinated PP about 5000 nm. Nearly the same barrier efficiency was measured for both plasma- and chemically fluorinated samples.
TiN hard coatings have been prepared by unbalanced magnetron (UBM) sputtering and cathodic arc deposition using uni- and bipolar pulsed bias voltages. For UBM sputtering using a unipolar pulsed bias voltage the average substrate bulk temperature Ts was reduced to 220 °C without considerable loss of microhardness and adhesion by variation of the pulse parameters. Determination of the average energy Ep delivered to the growing film per deposited particle leads to values lower than the critical transition energy (150 eV atom-1) between open porous and dense coatings. Using a bipolar pulsed bias voltage Ts decreased with increasing duration ton+ of the positive bias pulse. It was found that Ep increased with increasing ton+ up to values found for d.c. bias voltage. The coatings prepared using a bipolar pulsed bias voltage at low Ts are dense and in compressive stress with acceptable microhardness and adhesion. First results of the investigation of TiN coatings prepared by cathodic arc deposition using unipolar pulsed bias are given.
Template Electrodeposition of Nanowire Arrays on Gold Foils Fabricated by Pulsed-Laser Deposition
(1995)
Rapid resorbable, glassy crystalline materials on the basis of calcium alkali orthophosphates
(1995)
Neben Hydroxylapatit (HAp) findet verstärkt auch Tricalciumphosphat (TCP) Anwendung als Knochenersatzmaterial. In der Literatur finden sich widersprüchliche Angaben zur Löslichkeit von TCP. Bedingt durch unterschiedliche Darstellungsverfahren ergeben sich verschiedenartige Materialbeschaffenheiten, die sich erst nach der Implantation durch ein differenziertes Resorptions-verhalten dokumentieren (partikulärer Abbau, chemischer Lösungsprozeß). Zur Klärung derartiger Zusammenhänge in vitro wurden 2 Methoden zur Bestimmung des Lösungsverhaltens untersucht. Dafür wurden TCP-Proben aus verschiedenen Rohstoffen dargestellt, nach unterschiedlichen Temperaturregimen behandelt und/oder einer Nachbehandlung mit Phosphorsäure unterzogen.
Diese Materialien wurden vor allem mittels Röntgenpulverdiffraktometrie und Rasterelektronenmikroskopie charakterisiert. In anschließenden Löslichkeitsuntersuchungen wurden die optimalen Versuchsparameter (Lösungsmittel, Konzentration, Verhältnis Lösungsmittelmenge zur Lösungsoberfläche usw.) sowie geeignete Meßgrößen (Masseverlust, Ionenkonzentration) ermittelt. Die In-vitro-Löslichkeit erwies sich bei sorgfältiger Auswahl der Versuchsbedingungen als sehr wirkungsvolle Charakterisierungsmöglichkeit, die auf synthesebedingte chemische und morphologische Unterschiede sehr empfindlich reagiert.
Translated Abstract
Resorbable bone substitution on the basis of calcium phosphates
Besides hydroxyapatite (HAp), tricalcium phosphate is increasingly being used as bone substitution material. In literature there are contradictory claims of the TCP solubility. As a result of are contradictory claims of the TCP solubility. As a result of different manufacturing processes there are altered material properties, which are documented by different resorption behaviour especielly after implantation (particle separation, chemical solvatation). To clarify of such in vitro connections two methods for determining the solubility were investigated. Especially for this case, TCP samples prepared from different raw materials were synthesized. These samples were given different heat treatments and/or posttreatments with phosphoric acid.
The materials were characterized above all by using X-ray powder diffraction method and scanning electron microscopy. Following investigations of the solubility lead to optimized testing parameters (solvent, concentration, ratio of solvent's quantity to sample surface, etc.) as well as qualified test parameters (lost of weight, ion concentration). When the test conditions were carefully selected, the in vitro solubillity was proved to be a very effective possibility of materials characterisation which is also very sensitive regarding chemical differences caused by synthesizing or morphological differences.
Integrity of the "POLLUX" cask for final disposal: Experimental results of the mechanical tests
(1995)
Plasma Spreyed Coatings of Calcium Titanium Phosphate - A New Generation of Bioactive Coatings
(1995)
EXAFS investigation of an intermediate crystalline phase in TiO2-rich strontium borate glasses
(1995)
TEM Characterization of the Interface Quality of MOVPE Grown Strained InGaAs/GaAs Heterostructures
(1995)
Optimiertes Bauteilverhalten
(1995)
A simple preparation of Cd17S4(SCH2CH2OH)26 clusters in aqueous solution leads to the formation of colorless blocky crystals. X-ray structure determinations revealed a superlattice framework built up of covalently linked clusters. This superlattice is best described as two enlarged and interlaced diamond or zinc blende lattices. Because both the superlattice and the clusters display the same structural features, the crystal structure resembles the self-similarities known from fractal geometry. The optical spectrum of the cluster solution displays a sharp transition around 290 nanometers with a large Absorption coefficient (~84,000 per molar per centimeter).
The BAM List serves as the basis for the BAM's substance-related prototype approvals for tank containers designed for the transport of dangerous goods; further to this, the list may also be used as a knowledge source for the approval of tank vehicles. Furthermore, it also serves as a reference for the material-related evaluation of other types of containers transporting dangerous materials.
This synoptic presentation of requirements for tanks to be used for the transport of dangerous goods is based on data stored in the BAM's TANKSAFE data base. This data reflects state of the art reliability engineering in this field of operations. For years it has formed a basis for the BAM in its responsibility for awarding prototype approvals for tank containers.
Durch die Entwicklung des Schichtverbundkörpers wurde eine Probengeometrie geschaffen, die sowohl Zerspan- und Streifenziehversuche als auch Modellverschleiß-, Bauteils-, metallographische und mikroanalytische Untersuchungen an einem Körper erlaubt. Neben den Labor und Feldversuchen waren auch umfangreiche Rauheits-, Eigenspannungs- und Texturmessungen Schwerpunkte der Untersuchungen.
Ziel der Untersuchung war, beliebige Dämpfungsverläufe in die allgemeinen, im Zeitraum formulierten Bewegungsgleichungen zu implizieren und vor allem die numerischen Konsequenzen der Resultate aufzuzeigen. Ferner wird ein Lösungsverfahren entwickelt, das mittels komplexen Streifigkeitsansätze unter Verwendung zeitversetzter Belastung eine vollständige Erfassung allgemeiner Dämpfungsvorgaben gestattet.
Hier wird der chronologische Verlauf der Kristallisation verfolgt. Sie beginnt mit den thermodynamischen Grundlagen der Keimbildung und des Wachstums, stellt anschließend Wachstumsformen in der Frühlphase der Kristallisation vor und behandelt schließlich die spärolithische Hauptkristallisation sowie die sogenannte Nachkristallisation.
Es werden 15 Merkmale vorgestellt, die als Einzelmerkmale und als Merkmalskombination an einem Schweißnahtkatalog mit über 500 Fehlerabbildungen erprobt worden. Die Beurteilung der Merkmale erfolgt im eindimensionalen Fall über das Gütemaß und den Bhattacharyya-Koeffizienten. Im mehrdimensionalen Merkmalsraum wird zur Beurteilung der Merkmalskombination zusätzlich die Hauptkomponententransformation eingesetzt.
NMR is a powerful method for structure elucidation and determination of polymers in solution. Soluble polymers can be studied by high resolution techniques - just äs small molecules - provided there is sufficient segmental motion to average out some of the linebroadening effects. The resonance lines remain broader, however, which can result in peak overlapping, especially for proton spectra. Carbon NMR is favoured in this field because of the larger spectral range and the feasibility of getting single lines by proton broad-band decoupling. One particulariy important use of NMR is the determination ofthe microstructure of the polymer chain.
The application of high resolution NMR to solid polymers was not possible until the development of techniques like magic angle spinning, high power proton decoupling and cross polarization. The linebroadening effects in thermoplastic and duroplastic polymers, however, are only reduced to some extent. The spectra show relatively broad lines, with typical linewidths of 100 - 500 Hz, which are roughly 10 to 100 times larger than in the liquid state. Different from thermoplastic and duroplastic polymers the spectra of elastomers have a much better resolution if the measurements are performed well above the glass transition temperature. This condition is fulfilled at room temperature for many elastomers. Above Tg linebroadening effects are averaged out by segmental motions, comparable to the liquid phase. By raising the temperature the resolution can be increased further which especially improves the spectra of elastomers with relatively high glass transition temperatures.
Filiers can influence the linewidth of the spectra. The effect is twofold. First, the filier particies, e.g. carbon black, introduce microscopic inhohogeneities by susceptibility variations. Second, the molecular mobility ofthe polymer chains is reduced. Both effects can be averaged out to a great extent by magic angle spinning and high power decoupling, however. Therefore the filier has no detrimental influence on the resolution of the solid-state elastomer spectra. As a consequence, no decomposition procedures are necessary prior to the NMR investigation. The sample can be measured in its original molecular state.
This was the starting point for a thorough and comprehensive investigation of filled elastomers using the solid state technique in order to find out the possibilities and limits. The experiment tumed out to be very suecessfül. This lead us to the idea to put all the spectra together in form of a spectra catalogue.The collection contains the most important Standard and special commercial rubber types. In order to complement the solid state NMR part two chapters on blends and thermoplastic elastomers are added. Proton and carbon solution spectra of the raw rubbers are also included. Especially important is the interpretation ofthe spectra, in order not to display only "fingerprints".