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Measurements of Photoluminescence Quantum Yields of Scattering LED Converter Materials
No full textHow to Get it Right with the Absolute Measurement of Photoluminescence Quantum Yields of Scattering LED Converter Materials Saskia Fiedler+,a, Florian Frenzel+,a, Christian Würth a, Isabella Tavernaro a, Michelle Grüne c, Stefan Schweizer c,d, Axel Engel e, and Ute Resch-Genger a* a Division Biophotonics, Federal Institute for Materials Research and Testing (BAM), Richard-Willstaetter-Strasse 11, D-12489 Berlin, Germany; email: [email protected] b Present address: Photonic Materials, NWO-Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands c Faculty of Electrical Engineering, South Westphalia University of Applied Sciences, Lübecker Ring 2, 59494, Soest, Germany d Fraunhofer Application Center for Inorganic Phosphors, Branch Lab of Fraunhofer Institute for Microstructure of Materials and Systems IMWS, Lübecker Ring 2, 59494, Soest, Germany e Schott AG Technical Services, Hattenbergstrasse 10, D-55122 Mainz, Germany Optical measurements of scattering materials such as luminescent nano- and microparticles and phosphors dispersed in liquid and solid matrices play an important role in energy conversion, solid-state lighting, medical diagnostics, and security barcoding. A key performance parameter is the photoluminescence quantum yield QY, i.e., the number of emitted per number of absorbed photons. QY of transparent luminophore solutions can be obtained relative to a fluorescence QY standard of known QY, meanwhile available as certified reference materials.[1] The determination of QY of scattering liquid and solid samples like nanoparticle dispersions, phosphors, and optoceramics requires, however, absolute measurements with an integrating sphere setup. Despite the need for reliable absolute QY measurements, no interlaboratory comparison (ILCs) on measurement uncertainties has been performed and scattering standards with known QY are not available. We present the results of an ILC of 3 labs from academia and industry on measurements of transparent and scattering dye solutions and solid phosphors and converter materials like YAG:Ce optoceramics with commercial stand-alone integrating sphere setups of different illumination and detection geometries. Special emphasis was dedicated to the influence of measurement geometry, optical properties of the blank for determining the number of incident photons absorbed by the sample, and sample-specific surface roughness. Matching QY values could be obtained for transparent dye solutions and scattering dispersions with a blank with scattering properties closely matching those of the sample, QY measurements of optoceramic samples with different blanks revealed substantial differences of more than 20 %. Based on our data, we recommend non-absorbing blank materials with a high reflectivity (>95 %) such as a 2 mm-thick PTFE target placed on the sample holder as blanks
Thermografie zur Vergleichbarkeit von Emissionsmessung im 3D-Druck
No full textDie Bedeutung der Extrudertemperatur bei kleinen Desktop 3D Druckern der
Fused Filament Fabrication (FFF) Technologie auf die Emission von ultrafeinen
Partikeln im Druckbetrieb ist nicht zu unterschätzen.
Allerdings zeigen kommerzielle 3D Drucker häufig eine systematische
Temperaturabweichung zum Sollwert, d.h. die eingestellte Temperatur weicht
von der tatsächlichen Temperatur ab. Da die Partikelemission meist
temperaturabhängig ist, ist eine genaue Messung der tatsächlichen
Extrudertemperatur für den Vergleich von Emissionsdaten aus
unterschiedlichen Druckermodellen relevant
Investigation of Fe-Ni-O nanoparticles for water splitting
No full textThis study investigates the effect of varying iron-to-nickel ratios on the catalytic performance of Fe-Ni oxide nanoparticles (NPs) for the oxygen evolution reaction (OER). Addressing the issue of high energy wastage due to large overpotentials in OER, we synthesized and characterized different NP catalysts with different Fe: Ni oxide ratios. Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Spectroscopy (EDS), and X-ray Diffraction (XRD) were employed to determine the morphology, elemental and phase composition of the NPs. Furthermore, in-depth profiling with X-rayPhotoelectron Spectroscopy (XPS) and Hard X-ray Photoelectron Spectroscopy (HAXPES) revealedthat iron predominantly exists as oxide, while nickel exhibits both metallic and oxidic forms depending on the Fe content. XPS indicated an enrichment of iron at the NP surface, whereas HAXPES and EDSdata agreed on the bulk stoichiometry
Geruchs- und emissionsarme Produkte für eine gesunde Innenraumluft - Entwicklung von Anforderungen für den Blauen Engel bei innenraumrelevanten, großflächigen Produkten
No full textGerüche in Innenräumen können belästigend wirken und das Wohlbefinden sowie die Gesundheit beeinflussen. Hauptziel der Untersuchungen ist es zu prüfen, ob die Vergabekriterien des Blauen Engels für die Produktgruppen „Elastische Bodenbeläge“ (DE-UZ 120) und „Emissionsarme Bodenbeläge, Paneele und Türen aus Holz und Holzwerkstoffen für Innenräume“ (DE-UZ 176) um geruchsrelevante Aspekte ergänzt werden können. Dies ist erstrebenswert, da Untersuchungen in Vorgängerprojekten gezeigt haben, dass die gemessenen Emissionen untersuchter Produkte zwar abnehmen, die Geruchsbelastung jedoch in etwa gleichgeblieben ist. Die Ergebnisse der Untersuchungen zeigen, dass es möglich ist Anforderungen an den Geruch der Produkte zu stellen.
Ferner wird untersucht und gezeigt, dass die bislang vorläufig festgelegte Schwelle einer empfundenen Intensität von 7 pi für die Zulassung von Bauprodukten gemäß Schema des Ausschusses zur gesundheitlichen Bewertung von Bauprodukten (AgBB) und Blauer Engel, als Beurteilungsmaßstab geeignet ist. Der im AgBB-Schema zugrunde gelegte Zusammenhang zwischen der geruchlichen Zumutbarkeit und der empfundenen Intensität kann mit den durchgeführten Messungen untermauert werden. Es kann gezeigt werden, dass bei Tests mit großen, ungeschulten Personengruppen etwa 70% der Probandinnen und Probanden Produkte mit einer empfundenen Intensität von bis zu 7 pi geruchlich als zumutbar empfinden.
Zur Bewertung der empfundenen Intensität wird ein Vergleichsmaßstab verwendet. Die Einhaltung konstanter Bedingungen für die Temperatur und die relative Feuchte bei den Messungen ist von großer Bedeutung, da diese einen Einfluss auf die Messergebnisse haben. Daher werden Untersuchungen bei unterschiedlichen Temperaturen und relativer Luftfeuchte, die mit einer eigens dafür gebauten kleinen raumlufttechnischen Anlage eingestellt werden können, durchgeführt. Die Ergebnisse belegen, dass die Einhaltung konstanter Prüfbedingungen wichtig ist und zeigen deren Einfluss auf die Geruchwahrnehmung.
In einem neuen Luftqualitätslabor der HTW Berlin können Innenräume unter standardisierten Bedingungen geprüft werden. Es werden vergleichende Messungen mit Emissionsprüfkammertests durchgeführt, um zu prüfen, ob ähnliche Ergebnisse erreicht werden können. Das Ziel ist es, die Räume später für sensorische Messungen mit verschiedenen Ausstattungen zu nutzen.
Das Vorhaben baut auf den Ergebnissen der Vorhaben UBA Texte 35/2011 „Sensorische Bewertung der Emissionen aus Bauprodukten – Integration in die Vergabegrundlagen für den Blauen Engel und das Bewertungsschema des Ausschusses zur gesundheitlichen Bewertung von Bauprodukten“ (Müller, 2011) und UBA Texte 92/2019 „Emissions- und geruchsarme Bauprodukte für energieeffiziente Gebäude – Entwicklung von Anforderungen und Konzepten für den Blauen Engel aus Klimaschutzsicht“ (Müller, 2019) auf
Tracking nanoplastics in drinking water: a new frontier with the combination of dielectrophoresis and Raman spectroscopy
No full textDetection of micro- (MPs) and nanoplastics (NPs) in food and environmental matrices has been gaining relevance due to their potential toxicological effects on human health. While MPs have been detected in a wide range of complex matrices, suitable methods for the characterization and chemical identification of NPs are still lacking, primarily due to significant methodological challenges associated with their nano-specific physiochemical properties, including size distribution (1 nm – 1 µm), dynamic surface chemical changes, and carbon-based composition, which complicate their detection compared to engineered nanomaterials. To overcome the traditional limitations of spectroscopic techniques in terms of spatial resolution and sensitivity at the sub-micrometer level, a novel label-free methodology is presented for specifically identifying the chemical composition of NPs directly in suspension by combining Raman spectroscopy with dielectrophoresis (DEP). Using a custom-built device, small volumes of NPs are injected into a dielectrophoretic cell and locally trapped by DEP forces to fill the Raman confocal volume, facilitating their detection and identification, and providing high signal-to-noise ratio Raman spectra for more reliable analysis. This approach was successfully applied to both Milli-Q water and a commercial brand of drinking water, enabling the rapid identification of various types of NPs with different sizes and polymer compositions at concentrations as low as 20 µg/mL. These included certified reference polystyrene beads ranging from 800 to 60 nm in diameter, as well as polydisperse NPs, more representative of real samples in terms of size distribution and polymer type, such as polyethylene (450 nm), polypropylene (180 nm), and polyethylene terephthalate (100 nm). Moreover, the chemical fingerprint of each NPs was thoroughly investigated and compared with the corresponding bulk polymers, highlighting possible changes in the Raman bands due to surface oxidation or nanometer-scale effect. Therefore, this innovative method can be considered a valuable approach for addressing gaps in the detection and identification of NPs, as well as for monitoring their dynamic phisiochemical changes in real matrices
1 + 1 ≠ 2 – Laminate Materials Meet Flame Retardancy
No full textMain message: Fire tests monitor the specific response of defined test specimens but are used to assess materials’ fire risks. The weakness of this simplification becomes obvious for laminate materials. The talk delivers inspiring food for thought in discussing the fire behaviour of laminates. The fire behaviour must not be expected to be a simple superposition. The design of laminate can generate fire risks as well as give birth to flame retardancy. Introduction Bench-scale fire testing monitors the reaction-to-fire response of well-defined test specimens in certain fire scenarios. Results are often discussed as kind of material properties; indeed, the fire risks of materials are assessed. The weakness of this simplifying concept becomes obvious when it comes to investigating material systems such as all kind of laminate materials. The talk delivers inspiring food for thought sketching the complex and sometimes surprising fire behaviour of laminates. Experimental The polymer analysis, thermal analysis, and investigation of fire behaviour were performed according to the state of the art, mostly in accordance with the ISO standards. We fulfil high quality standards in terms of maintenance, calibration, participation in round robins, and so on. Work steps such as compounding of the materials or injection moulding of test specimen were outsourced or done with partners that have the relevant core competence. The presentation is based on the conclusions and concrete results of projects performed in the group of the author, whose experimental is described in the corresponding scientific papers in detail.[1-3] Results and Discussion Examples show that the fire behaviour of laminates must not be expected to be a simple superposition of the fire behaviour of the individual materials. Indeed, laminate effects can be crucial and influence the flammability relevantly. The design of the laminate can generate fire risks as well as give birth to synergistic flame retardancy. Veneered wood, lacquered products, or foil laminated materials are sketched to illustrate the topic with its potential and challenges. Glued samples consisting of two plates of the same material are discussed to generate some basic understanding as well as to investigate the fire behaviour of glued materials. The impact of the glue line on the burning behaviour of different polymeric materials such as bisphenol A polycarbonate, polymethylmethacrylate, and wood differs remarkably.[2] Further, the role of the glue including but not limited to using flame retarded glues is scrutinized. Making the best out of this understanding we have proposed to concentrate flame retardancy in the top layer.[1, 3] To achieve optimum flame-retardant effect or flame retardancy without disturbing the property profile of the core, flame retardants are strategically concentrated in the surface layer of thermoplastic materials with a laminate structure. Several systems increasing the charring and forming a residual protective layer are identified showing a synergistic effect compared to homogenously flame retarded test specimen. This research presented a promising solution for reducing the use of flame retardants without sacrificing fire performance or mechanical properties, offering significant advantages for industrial applications
Flame Retardant Polylimonen Carbonate: Material Innovation as a Game Changer
No full textMain message: This research seeks to understand and identify the most promising approaches to enhance the flame resistance of poly(limonene carbonate) (PLimC). Furthermore, the goal is to develop a PLimC-based material that incorporates halogen-free flame retardants (FRs) that are not only highly effective but also environmentally sustainable, contributing to the advancement of greener materials for safer use. Introduction The plastic industry depends on fossil-based materials, causing environmental concerns. PLimC, a sustainable polymer derived from limonene and CO₂ [1], offers a promising alternative. Its use in fire safe applications underscores the need to optimize its performance. This study evaluates halogen free FRs to identify and understand the most promising approaches to enhance PLimC’s flame resistance, aiming to improve fire safety and support eco-friendly material development. Experimental: This study has as its main task to conduct experimental evaluations to analyze the thermal properties, flammability, and fire behavior of each system. Pyrolysis, together with the evolved gases of the samples, were analyzed by thermogravimetric analysis coupled with a FTIR spectrometer. The energy content was determined by using a bomb calorimeter. The flammability of the samples was assessed by the reaction to small flame tests such as the UL 94 burning chamber and limiting oxygen index (LOI). The burning behavior in forced flamed conditions was evaluated using the cone calorimeter. Results and Discussion: Thermal properties were first evaluated to gain a deeper understanding of the pure PLimC thermal stability and fire behavior. This analysis builds on PLimC's structural similarity to polycarbonate (PC), due to its carbonate group, and to polyolefins (PO), due to its aliphatic limonene-derived segment, providing insights into optimizing PLimC for sustainable, fire-safe applications. The initial results, which defined our starting point, showed that the LOI of PLimC was 17.2%, very close to that of PO such as polyethylene (PE) and polypropylene (PP) (~18%). In contrast, PC has a higher LOI of ~24%. Additionally, PLimC did not produce any char (0 wt.-%), similar to PO, whereas PC forms char due to its phenolic structures. The effective heat of combustion of PLimC, measured using bomb calorimetry, was determined to be 31.1 MJ/kg. This value is comparable to that of PC (~30 MJ/kg) but significantly lower than PO (~44 MJ/kg). These findings, which demonstrated similarities to both PO and PC, prompted the evaluation of various commercially available FRs at standard market concentrations. Four halogen-free FR systems were chosen for evaluation: 1. mixture of APP (20 wt.-%) + pentaerythritol (10 wt.-%) as an intumescent system [PLimC / APP / Penta], 2. mixture of the phosphorus compound PX200® (16 wt.-%) + PTFE (0.4 wt.-%) as antidripping [PLimC / PhosC / PTFE], 3. metal hydroxide ATH (50 wt.-%) [PLimC / ATH], and the potassium sulfonate salt Bayowet® (0.4 wt.-%) [PLimC / SulfS]. The concentrations were decided according to the standards used in the industry for polyolefins (system 1 and 3), the mixture polycarbonate / ABS (system 2) and polycarbonates (system 4). PLimC has the usual behavior of a non-charring specimen (fast burning and high peak of heat release). ATH proved to be the most effective flame retardant, achieving the biggest reductions in the effective heat of combustion (EHC) and total heat evolved (THE), as demonstrated by cone calorimeter measurements. Additionally, ATH achieved the highest increase in the LOI (17.1% —> 26.0%). With these results, we understood that the FRs commonly used with polyolefins (at concentrations standard in the industry) exhibit similar behavior in terms of flammability and flame retardancy when applied to PLimC. Although ATH has proven to be an effective flame retardant for PLimC, offering a sustainable solution due to its abundance, non-toxicity, and low environmental impact, we aim to explore bio-based flame retardants to further enhance the material’s sustainability. Since phytic acid salts [2] and lignin [3] have demonstrated flame retardant efficacy in polyolefins, we believe these compounds could also perform well in our system. Phytic acid salts are particularly promising due to their high phosphorus content—and in some cases, nitrogen—which promotes char formation and enhances flame retardancy. Lignin’s unique ability to promote charring could significantly improve flame retardancy, due to the fact that PLimC like polyolefins, lacks inherent char formation. By integrating these bio-based flame retardants, we move closer to developing a fully sustainable material that aligns with the Sustainable Development Goals of the United Nations, contributing to a greener and more resilient future
Data-Driven Materials Science: Reproducibility and Standardization
No full textAdvancing development and digitalization in materials science requires to focus on quality assurance, interoperability, and compliance with FAIR principles. Semantic technologies offer effective solutions for these challenges by enabling the storage, processing, and contextualization of data in machine-actionable and human-readable formats – essential for robust data management.
This presentation highlights the PMD Core Ontology 3.0 (PMDco 3.0), developed specifically for the field of materials science and engineering, and its implementation within generic knowledge representation frameworks. Demonstrators such as standardized mechanical testing, material processing workflows, and the Orowan Demonstrator exemplify the ontology’s practical applications. The use of graph patterns, able to be compiled into rule-based semantic shapes, supports a unified and automated approach to managing heterogeneous experimental data across domains
Differential Mobility Analysis with Acoustic Ion Manipulation (AIM)
No full textIon mobility analyses provide complementarity to mass spectrometry in analyte ion identification through the introduction of a higher-pressure separation modality. The recently discovered acoustic ion manipulation (AIM) phenomenon, which exploits unique behaviors of ions in acoustic fields, presents a novel, electric-field-free means to distinguish ions by mobility. In one form of AIM, a static pressure field in an ultrasonic resonator causes a displacement of the ion stream toward the node region, when initially directed toward the antinode. When the static field strength falls below the threshold for all ion deflection, the partitioning reflects ion-specific acoustic mobilities or acoustic radiation impedance. This study demonstrates ion-oriented mobility separation with the AIM approach for mass-spectrometric analysis.
An Orbitrap mass spectrometer was used to record ion signal variations as a function of acoustic field strength. An acoustic pressure source with a transducer–reflector configuration was used to generate a standing acoustic wave for partial ion deflection. The drive frequency was swept near resonance to modulate the static pressure field. An alternating-current (AC) plasma discharge source was used to produce an ion beam directed toward an antinode of the resonant structure and later deflected into the mass spectrometer inlet with the acoustic field. Several small molecule analytes, including methanol, ethanol, acetone, and toluene, were doped in the discharge gas to distinguish ions formed in the source from those produced in transit to the MS inlet.
An ion beam, offset relative to the inlet capillary of the mass spectrometer, yielded minimal ion detection in the absence of the resonant acoustic field. A sweep of the frequency near resonance induced a low–high–low transition in the static pressure within the resonator. Consequently, the total ion signal as a function of drive frequency resembled a horn gain curve, which is commonly recognized as a key characteristic in ultrasonic transducer design. Maximum ion signal was attained at the resonance frequency, while a pronounced minimum occurred at the anti-resonance frequency. Analysis of drive frequency response curves for distinct ion peaks revealed that source-generated ions displayed a congruent pattern to the overall ion count, thereby suggesting the formation of clusters prior to the vacuum region of the mass spectrometer. A finer frequency scan near the resonance region differentiated these clusters. For instance, response curves for toluene-related ions are slightly deviated from those associated with alcohols. Notably, a series of ions, presumably originating from an identical chemical precursor, manifested an entirely distinctive drive frequency response; their maximal signal occurred at a frequency not associated with any characteristic of the acoustic system or its electronics. The frequency response curves of the ions allowed implementation of a modified cross-correlation (mXcorr) algorithm to categorize ions according to chemical origin or clustering. The use of frequency, rather than the transducer voltage/power, offers the advantage of electronically measuring the horn gain curve in tandem with ion-specific analysis. This gain curve subsequently serves as a reference to decode latent chemical information for enhanced analytical accuracy
N-aminophthalimide as a novel UV-stabilizer to promote physico-mechanical properties of highdensity polyethylene (HDPE)
No full textThis study aimed to evaluate the efficacy of Naminophthalimide (NAP) as a novel UV-stabilizer for highdensity polyethylene (HDPE) in improving its physicomechanical properties under UV exposure. NAP was synthesized by interaction between phthalimide and hydrazine hydrate. It was incorporated into HDPE with different weight ratios (1, 1.5, 2, and 3%), and its performancewas compared with Hostavin as a traditional UV stabilizer. The HDPE composites were exposed to UV irradiation for different periods (7 and 14 days) to evaluate their photodegradation behavior. Tensile strength, elongation at break were assessed before and after UV exposure. Also, oxidation induction time (OIT), melt flow rate (MFR), Vicat softening temperature were evaluated. Hostavin incorporation reduced tensile strength from 22.36 to 20.62MPa at higher concentrations. It has been found that 3% Hostavin, significantly improved elongation at break, increasing from 423% to 1,170%, suggesting enhanced flexibility. In contrast, NAP increased tensile strength to 22.9MPa and moderately enhanced elongation but slightly declined at 3%due to potential over-stabilization. Under UV exposure, retained tensile strength and elongation was improved with stabilizer content, which increasing tensile strength retention. The HDPE that containing NAP showed enhanced UV resistance and superior retention of mechanical properties compared to Hostavin