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Eingeladener Vortrag
- nein (250)
The flame retardant effect of zinc sulphide (ZnS) in plasticised poly(vinyl chloride) (PVC-P) materials was investigated. PVC-P containing different combinations of additives such as 5% ZnS, 5% of antimony oxide (Sb2O3) and 5% of mixtures based on Sb2O3 and ZnS were compared. The thermal degradation and the combustion behaviour were studied using thermogravimetry (TG), coupled with FTIR (TG-FTIR) or with mass spectroscopy (TG-MS), and a cone calorimeter, respectively. A detailed and unambiguous understanding of the decomposition and release of the pyrolysis products was obtained using both TG-MS and TG-FTIR. The influence of ZnS, Sb2O3 and the corresponding mixtures on the thermal decomposition of PVC-P was demonstrated. Synergism was observed for the combination of the two additives. The combustion behaviour (time to ignition, heat release, smoke production, mass loss, CO production) was monitored versus external heat fluxes between 30 and 75 kW m-2 with the cone calorimeter. Adding 5% of ZnS has no significant influence on the fire behaviour of PVC-P materials beyond a dilution effect, whereas Sb2O3 works as an effective fire retardant. Synergism of ZnS and Sb2O3 allows the possibility of replacing half of Sb2O3 by ZnS to reach equivalent fire retardancy.
XTEM and TFXRD investigations of ohmic Ti/Al/Ti/Au/WSiN contacts on AlGaN/GaN HFET layer systems
(2002)
The microstructural features of the high-temperature-stable ohmic contact system Ti/Al/Ti/Au/WSiN on AlGaN/GaN were investigated using analytical transmission electron microscopy and thin film x-ray diffraction. For two typical rapid thermal annealing steps at 750 °C (non-ohmic behaviour) and 850 °C (ohmic behaviour) the intermetallic phases at the metal-semiconductor interface are presented. Increased annealing leads to the transformation of an Al2Au-AlAuTi phase mixture to a mixture of Al2Au-Al3Au8 phases and the formation of Ti-Al-nitride layers at the interfaces. In light of these results the electrical contact properties are discussed.
XTEM and TFXRD investigations of ohmic Ti/Al/Ti/Au/WSiN contacts on AlGaN/GaN HFET layer systems
(2002)
The microstructural features of the high-temperature-stable ohmic contact system Ti/Al/Ti/Au/WSiN on AlGaN/GaN were investigated using analytical transmission electron microscopy and thin film x-ray diffraction.
For two typical rapid thermal annealing steps at 750 ◦C (non-ohmic behaviour) and 850 ◦C (ohmic behaviour) the intermetallic phases at the metal–semiconductor interface are presented. Increased annealing leads to the transformation of an Al2Au-AlAuTi phase mixture to a mixture of Al2Au-Al3Au8 phases and the formation of Ti-Al-nitride layers at the interfaces. In light of these results the electrical contact properties are discussed.
What is BAM?
(2002)
VOC/SVOC-Emissions from materials for flooring installation (primer, screed, adhesive, floor covering) were measured by means of emission test chambers and cells over a time period of at least 28 days at 23 C, 50 % relative humidity and an area specific air flow rate of q = 1.25 m³/m²h. Single components were tested in comparison to three complete structures (same concrete, primer, screed, adhesive) with different types of floor covering (PVC, carpet, linoleum). Sorption into concrete/screed and different sealing by the flooring materials affected the emissions from the complete structures. The complete structures with linoleum and PVC showed the same emissions and emission rates as the flooring materials alone. Emissions from the carpet-covered structure resulted mainly from the lower layers. For two adhesives the formation of secondary emissions (aldehydes and organic acids) was observed starting after the standard testing time of 28 days.
Nonequilibrium vibrational excitations of para-nitroaniline (PNA, 4-nitroaniline) occurring after internal conversion from the photoexcited charge transfer state are studied by picosecond anti-Stokes Raman scattering. Vibrational excess populations with distinctly different picosecond rise and decay times are found for a number of modes with frequencies between 860 and 1510 cm1, including the overtone of a non-Raman active mode. A nonthermal distribution of vibrational populations exists up to about 6 ps after photoexcitation. The time-resolved experiments are complemented by steady-state infrared and Raman measurements as well as calculations based on density functional theory, providing a detailed analysis of the steady-state vibrational spectra of PNA and two of its isotopomers. A weakly Raman active vibration at about 1510 cm1 displays the fastest rise time and a pronounced excess population andthusrepresents the main accepting mode. We suggest that an out-of-plane mode giving rise to the overtone Raman band at this frequency acts both as coupling and accepting mode in the internal conversion process.
The results and execution of many full scale fire engulfment tests on 3.6 and 4.85 m³ LPG tanks, protected with thin sublimation and intumescent coatings, mineral wool with steel jackets, vermiculite coatings and water spray systems, are presented.
Additional furnace tests with coated steel plates have been carried out to optimize the necessary coating thickness.
Similarly, an overview of the test conditions for the recognition based on technical rules and BAM requirements for fire protection systems of LPG tanks will be shown and explained.
When the internal pressure reaches the vessel bursting pressure a violent tank rupture, fragmenting of the shell and spontaneous release of the content are the consequences. In case of LPG this event is called "boiling liquid expanding vapour explosion (BLEVE)" with expanding fireball as an additional severe consequence.
For this reason the sufficient fire protection of LPG vessels is an important item.
The tests demonstrated sufficient vessel safety during 90 minutes of a full fire engulfment.
It will also be shown that the examinations and results are transferable to bigger tanks.
The transferability of the test results is illustrated by diagrams which show the dependence of the coating thickness against the shell thickness of the tank.
All tested tanks were equipped with pressure relief valves (PRVs) and partially filled with propane.
VDI/VDE-Guideline 5570 - The First Comprehensive Standard on Characterization and Testing of POF
(2002)
Use of 3D Micro Tomography for the Investigation of the Mechanical Properties of Cellular Metals
(2002)
Unusual relaxation behavior of water inside the sodalite cages of faujasite-type molecular sieves
(2002)
Unusual relaxation behavior of water inside the sodalite cages of faujasite-type molecular sieves
(2002)
Broad-band dielectric spectroscopy (10-2 to 109 Hz) is applied to investigate the molecular dynamics of NaY, a zeolite of faujasite structure. A dc conductivity contribution and three relaxation processes were revealed in the dielectric spectra. The relaxation process in the high-frequency range ascribed to orientational fluctuations of water molecules inside the sodalite cages is studied in detail. As a main result it is found that its mean relaxation time has an unusual saddle-like temperature dependence, which obeys neither an Arrhenius nor a Vogel-Fulcher-Tammann law. A quantitative description was given on the basis of a model recently developed by Feldman et al. (J. Phys. Chem. B 2001, 105, 1845) to analyze the dynamics of water confined in nanoporous glasses. Reasonable values for the activation energies of orientational fluctuations and of defect formation as well as for the defect concentration were obtained.
Several colour-difference formulas such as CMC, CIE94, and CIEDE2000 have been developed by modifying CIELAB. These formulas give much better fits for experimental data based on small colour differences than does CIELAB. None of these has an associated uniform colour space (UCS). The need for a UCS is demonstrated by the widespread use of the a*b* diagram despite the lack of uniformity. This article describes the development of formulas, with the same basic structure as the DIN99 formula, that predict the experimental data sets better than do the CMC and CIE94 colour-difference formulas and only slightly worse than CIEDE2000 (which was optimized on the experimental data). However, these formulas all have an associated UCS. The spaces are similar in form to L*a*b*. © 2002 Wiley Periodicals, Inc. Col Res Appl, 27, 282-290, 2002; Published online in Wiley InterScience (www.interscience.wiley.com).
Introduction
Due to the long history of railroad companies around the world, varying means of examination according to the specifications for the different railroad components have been carried out based on the general industrial progress of the country [1-3]. For more than 50 years the application of customized ultrasonic techniques for the examination of railroad components has increased, in comparison to conventional ultrasonic techniques used until to the end of 20th century. In this traditional atmosphere some accidents have disturbed the silent harmony of companies involved in the production of critical parts. More than ever high speed modern trains require modern and advanced examination techniques [4-8]. For practical application new ultrasonic techniques have been developed and optimized in co-operation with the German Railroad Company. In the present contribution the inspection of railroad axles will be described. The ultrasonic technique used for the examination is the phased array technique. The optimization of the phased array probes for the different geometries of the axles given was completed using a computer model for directivity calculations. In relation to the limited accessibility between wheel and brake angles of incidence for shear waves in the range between 28° and 72° are necessary.
During the examination of the axles a a considerable amount of ultrasonic data must be stored (storage of the digitized A-scans). However, due to economic aspects the evaluation of this data should be carried out in a very short time. The whole examination of one axle should not exceed 5 minutes. Therefore we have developed a special evaluation program adapted to the particular problematic of the axle inspection. The build up of the whole inspection system was done with partners from the industry like Krautkramer and a division of the Research Department of the Deutsche Bahn AG. In this consortium the Research Department of the Deutsche Bahn AG was responsible for the specification of the inspection problem, Krautkramer for the organization of the whole technical follow up and BAM for the development and optimization of the ultrasonic inspection technique as well as for the evaluation software. Some examples concerning the optimization process will be described in the present contribution.
The removal and accelerated corrosion monitoring of metal coating systems is of general interest in materials science
and engineering technology. The femtosecond and nanosecond laser ablation and delamination at 800 nm and 532 nm,
respectively, of anodic oxide layers on aluminium alloys in electrolyte contact were investigated. Laser-induced
modifications of the oxide layer resulted in an ionic contact between electrolyte and metal, which produced a current
transient and thus allowed the in-situ electrochemical monitoring of the modification. Oxide coatings with different
optical properties, almost transparent and opaque, were examined. The transparent anodic oxides showed contrasting
ablation mechanisms in the nanosecond and femtosecond pulse duration regime: nanosecond pulses caused spallation,
whereas femtosecond treatment led to ablation. Current signals measured in the transparent film were consistent with
light absorption below the metal-oxide interface and with film spallation. Irradiation of the opaque coating yielded ionic
current transients within the so-called shock-affected-zone of the oxide layer. This investigation provided insight into the
role of the penetration depth of light and the heat-affected zone, the extent of the shock-affected zone, and the defect
formation in the coating and at the solid-solid interface between metal and oxide.
Tribology of Advanced Ceramics III: Principles of solid lubrication - materials and mechanisms
(2002)
Composite liners (a geomembrane in intimate contact with a mineral liner) are frequently used to line landfills and contaminated sites. It is therefore very important to characterise the behaviour of these systems even under extreme conditions.
An investigation was undertaken to determine the influence of a mixture of concentrated organic contaminants on composite liner materials taken from test cells that had been dismantled after a 12-year permeation test.
The organic hydrocarbons had permeated the HDPE-geomembrane and had then migrated or had been adsorbed within the mineral liners, depending on their properties. The obtained concentration profiles of the contaminant mixture components indicate that the various mineral layer materials have selective retardation abilities which correspond to the different parameters of the organic compounds as well as of the mineral layer.
In addition, contaminant transport in the composite liners tested was modelled and the results of the model analysis compared with measurement data. An example (acetone) illustrates the calculated spatial and temporal contaminant concentration.
The composite liners investigated exhibit a very good sealing capacity against the concentrated organic contaminants used.
Disc brakes are widely used in cars, trains, and other vehicles. For understanding the basic processes occurring during the friction process, information on the surface topography of brake pads and discs is needed, in addition to information about chemistry and thermodynamics. In this paper, samples of pads and discs were analysed using white light interferometry. The topography of the surfaces was measured quantitatively. Using software tools described in a previous paper [Wear 248 (2001) 121], the distributions of area, height, and slope of the contact patches were computed. Characteristic properties of the contact patches were found to describe the influence of the test parameters such as friction power and testing time.
Thin Film Reference Materials for Thickness Measurement by XRF and GIXR in the Nanometre Range
(2002)
Thermal shock cycle experiments between room and cryogenic temperatures on polymer composites
(2002)
Feste Referenzmaterialien für die Spurenanalytik umweltrelevanter organischer Schadstoffe erfordern aufgrund der geringen thermischen Belastbarkeit der Analyten besondere Aufarbeitungsstrategien für die Herstellung repräsentativer Teilproben. Das in der Fachgruppe I.2 seit 1994 für diesen Zweck systematisch aufgebaute technologische Instrumentarium wird vorgestellt, und das im Laufe der Jahre angesammelte Know How wird anhand von Beispielen vermittelt. Das im Laboratorium I.21 entwickelte Qualitätssystem für eine optimale Logistik der Arbeitsabläufe der Probenherstellung und -verwaltung sowie für eine bedarfsgerechte Charakterisierung der Materialien wird ausführlich erläutert.
Bezüglich der Verwendung der Referenzmaterialien wird herausgestellt, daß es zwei gleichberechtigte Anwendungsrichtungen gibt: die interne Qualitätskontrolle mit zertifizierten Referenzmaterialien (ZRM, z.B. für die Methodenvalidierung) und die externe Qualitätskontrolle (Proficiency Testing = Kompetenzbewertung von Prüflaboratorien). Referenzmaterialien für das Proficiency Testing, die im Umweltbereich in viel größeren Stückzahlen umgesetzt werden können als ZRM, weisen bezüglich Homogenität und Charakterisierung die gleichen Qualitätskriterien wie ZRM auf. Diese Materialien haben - auch im internationalen Maßstab - stark an Bedeutung gewonnen.
Ein englisches Abstract gibt es nicht, aber eine Grobgliederung zur Vortragsankündigung:
This lecture includes:
· the technological and logistical aspects of reference material preparation and sub-sampling and subsequent sample management,
· appropriate measurement strategies for homogeneity and stability studies,
· the use of relevant statistical tests to evaluate those measurement data,
· the organisation of interlaboratory studies based on traceable measurements
PMMA and PC undergo photochemical aging leading to a gradual loss of material transparency and appearance during service life, which is desired to reach 50 years or more. Available artificial weathering test methods are unable to distinguish materials in terms of the speed of aging in outdoor use as roof materials. In order to design an appropriate accelerated or time-compressed test method, the 'worst case' scenario of the respective climatic conditions must be found. Therefore, samples of PMMA and PC were exposed to artificial weathering tests using different climatic conditions in terms of relative humidity and surface wetness. In the case of PMMA, it was found that water accelerates the photo degradation enormously. The fastest aging occurred when liquid water and UV radiation acted simultaneously on the sample surface and the PMMA reached its highest water content during weathering. In the case of PC, it was found that both vapour and liquid water speed up the photoaging, similarly to PMMA. But differently from PMMA, the worst case scenario for PC proved to be weathering conditions with high relative humidity. A test method has to be able to run artificial weathering under the different moisture conditions which can occur in the field.
The use of biodegradable bone substitutes is advantageous for alveolar ridge augmentation, since it avoids second-site surgery for autograft harvesting. This study examines the effect of novel, rapidly resorbable calcium phosphates on the expression of bone-related genes and proteins by human bone derived cells (HBDC) and compares this behavior to that of tricalciumphosphate (TCP). Test materials were -TCP, a newly synthesized chemical Ca2KNa(PO4)2 (material denominated R17), two glassy crystalline materials with a crystalline phase Ca2KNa(PO4)2 and in addition a small amorphous portion containing either magnesium potassium phosphate (material denominated GB14) or silica phosphate (material denominated GB9). HBDC was grown on the substrates for 3, 5, 7, 14 and 21 days, counted and probed for various mRNAs and proteins (collagen type I, osteocalcin, osteopontin, osteonectin, alkaline phosphatase and bone sialoprotein). All substrates supported continuous cellular growth for 21 days. At day 21, R17, GB9, TCP and GB14.
The functional expression of human bone derived cells grown on resorbable bioactive glass ceramics
(2002)
The fuctional expression of human bone derived cells grown on resorbable bioactive glass ceramics
(2002)
The focused ion beam technique - eine interessante Alternative, auch für konventionelle Werkstoffe
(2002)
The effectiveness of pressure relief devices on cylinders and tanks from the German point of view
(2002)
The effectiveness of pressure relief devices on cylinders and tanks from a German point of view
(2002)
Fire accidents during road and rail transport are not occurring very often. In particular fire accidents with total fire engulfment of tanks seem to be rather rare. Up to now authorities in Europe officially are of the opinion that in densely populated regions like Europe in the space of time between the beginning of a fire and the rupture of a tank measures could be taken like cooling of the heated tank surface and evacuation of the area probably affected by an explosion. Therefore, no requirements with regard to fire protection measures concerning transport tanks for land mode like the application of safety relief devices have to be met. Due to some catastrophic accidents being discussed in public even European authorities are considering the pros and cons of fire protection measures.
Nevertheless in sparsely populated regions and during transport at sea fire accidents have been looked at since ever as seriously dangerous events. Therefore, multi modal tanks for the transport of dangerous goods have to be fitted with safety relief devices. The delivery capacity of these devices has to be such that, in the event of total fire engulfment, the pressure inside the tank does not exceed certain limits.
With regard to accident records and results of fire tests it has to be stated that portable tanks may rupture violently, even if the tanks are fitted with pressure-relief devices adequately designed for the heat flux of full fire engulfment.
Therefore, the lecture will be dealing with the results of fire testing of tanks and conclusions to be drawn and considerations on:
the advantages of different fire protection measures for transport tanks,
the pros and cons of safety relief devices for cylinders and transport tanks,
improvement of regulations and recommendations.
X-ray stress analysis on crystalline materials is based on the determination of elastic lattice strains. The strains described by the shift of peak positions are converted to stresses by the means of theory of elasticity. The development of the sin2ψ-method of X-ray stress analysis introduced an enormous progress in X-ray stress analysis during the last decades. This report outlines some important elements of X-ray physics and fundamentals of theory of elasticity. The Standard measuring procedure are described and special experimental differences to the common powder diffractometry are outlined.
The adsorption of cetyltrimethyammonium bromide (CTAB) on a hanging mercury electrode is studied in various electrolyte systems and temperatures. A condensed film is formed at negative potentials and at room temperature only in the presence of KBr. The decrease of the temperature favors the formation of the condensed film. Hysterisis phenomena are observed during the potential scans at both directions. Capacity time curves at the potentials where the film is formed show a nucleation and growth mechanism, with induction time depending on potential, which has been investigated using Avrami formulation and has been explained as a progressive one-dimensional nucleation with constant growth rate. The nucleation rate increases while moving toward more negative potentials. A linear decrease of the capacitance with time was observed in some cases independent of the measuring potential in a relative large potential range. The different types of micelles can affect the adsorption of CTAB on mercury. An unusual capacitance transient observed at a very narrow negative potential range is attributed to the formation of hemicylinders. The condensed film in the presence of the other electrolytes is observed only at high concentrations (1 M) and very low temperatures (5°C).
Thermogravimetry (TG), thermogravimetry coupled with mass spectroscopy (TG-MS) and thermogravimetry coupled with Fourier transform infrared spectroscopy (TG-FTIR) were used to characterise the thermo-oxidative behaviour of two intumescent coating materials. The temperature dependence, the corresponding volatile products and the amount of residue of the different processes were determined. Using both TG-MS and TG-FTIR results in an unambiguous interpretation of the volatile products. Characteristics such as the influence of endothermic reactions, the release of non-flammable gases, the dehydrogenation enhancing the char formation and the stability of the cellular char were discussed in detail. It was demonstrated, that TG, TG-MS and TG-FTIR are powerful methods to investigate mechanisms in intumescent coatings and that they are suitable methods in respect to quality assurance and unambiguous identification of such materials.